- Datsun was very clever using the same 6-cylinder engine/transmission and drivetrain platform from 1970 to 1983. Not only did this make them easy to manufacture, but it lets an enthusiast mix parts from different years to create the perfect first generation Z. The secret is that the heavier 280ZX used physically identical 6-cylinder engines and transmissions from 1979 all the way through 1983, making them simple bolt-ins into earlier Z models. Since a great many 280Zs and ZXs are in junkyards what better time to breathe some life back into your car? So here is my formula for a very quick and fun 1970-78 Z along with tested performance tips. 240-260 folks would want to swap everything, while 280Z/ZX ZX people should keep their injection and ignition and change the drivetrain parts only.
FIRST - THE CAR
Unlike Chevy Chevelles of which several million were made, there were only 360,000 or so 1970-78 Zs made. After close to 40 years how many are still running? Sadly, rust, wrecks, and rebuilds have sidelined most of them over the decades. Despite the nostalgia I don't see a problem removing the old engine and drivetrain and replacing them with newer versions. Without your intervention the car would likely never see the street again.....it's your car after all.
If you want to find a base model to use for your fantasy racer, try to find one of the first 12,000 or so 240Zs made from 1970 to early 1971. These are identified by a "240Z" badge behind the side window and two grills on the rear hatch. These '70-71s were the lightest of all ZCARs, at about 2300 lbs, making them the best for performance buildups. Later models went to a round Z badge behind the side window and removed the hatch grills. Unfortunately the weight went up a few hundred pounds due to chassis strengthening.
1970 240Z F54 with P90 head, Nissan T5 5-speed, 4:11 differential
SECOND - the block
Datsun made several blocks over the years, varying in bore and casting methods. Compared to the 240Z L24, the 260Z L26 had a longer stroke, while the 280Z L28 had both a longer stroke and a larger bore. The way to identify the block is to look on the driver side of the engine, to the right of the motor mount. That's where they cast the block number.
BLOCK CASTING CODE
|L24 (1970 240Z)||2.4 liter||# E31 (flattop pistons)||E31|
|L24 ('71-73 240Z)||2.4 liter||# P30 (flattop pistons)||E88|
|L26 ('74 260Z)||2.6 liter||# P30 (flattop pistons)||E88|
|L28 ('75-80 280Z/ZX)||2.8 liter||# N42 (dished pistons)||N42, N47|
|L28 ('81-83 280ZX)||2.8 liter||# F54 (flattop/dished pistons, siamesed cylinders)||P79, P90, P90a|
Except for the turbo guys it seems that only since the late 1990s have have people focused on the F54 engines. Because of the Z's longevity these motors didn't show up in junkyards until then, well past the heyday of Z racing fever in the 1970s and early '80s. What people didn't realize is that minus power steering, AC, and other ZX plumbing the F54 was the most powerful L-series engine...it had to be to carry the heavier ZX. Personally, I like the idea of putting a late model F54 engine in a first generation Z and converting it back to carbs. Very retro, functional, and quick.
So I suggest using the last of the L28's: the 1981-1983 F54. It's cylinders are "siamesed" meaning that instead of coolant flowing between all the cylinders as on earlier models they are connected between 1-2, 3-4, 5-6 with cast webbing for more rigidity. There really isn't a special "turbo block", all Datsun did to make the F54 a turbo motor was to replace the flattop pistons with dished ones to lower compression and add a turbo head. It can be tricky determining exactly what combo is in your car as many have had the heads swapped over the years. First check the block code, then the head code between the 1st and 2nd spark plugs. Check out the head page to see which head came with which block. Sometimes you have to do a little detective work.
PISTONS The F54 motors with P79 heads ('81-83) have flat-top aluminum pistons. All other L28 engines/head combos (N42,N47,P90, P90a) came with dished pistons. In a performance engine, flattop pistons create a higher-quench mixture and allow for higher performance combustion chambers. Dished pistons are usually used to lower emissions.
HEADS The P79, P90 and P90a heads are the three heads found on F54 blocks and all have the same chamber volume (53.5cc). The P79 has diamond-shaped exhaust ports with steel liners that heat red-hot to reduce emissions, some say they reduce flow but I pulled a 13.9 1/4 mile with my carbureted P79 so I don't agree. The P90 and P90a had square exhaust ports identical to E88 and N42 heads, and my guru racer buddy says Nissan finally "got it right" on the P90 and feels it's the best flowing head out there. Its design incorporates the best features of all the heads: square exhaust ports, high-quench chambers, and steel seats. Check out my P90 and P79 pages for more modification details.
The 1975-80 L28 motors put out a rated 135hp while the 1981-83 L28 motors were 145 net. The little plate on the shock tower in the 1975-78 280Z's engine compartment may say 170hp SAE but thats gross HP...a sneaky 1970s way of saying 135 net.
THIRD - carburetion and fuel
The optimum stoichiometric air/fuel ratio for car engines is 14.7:1 (air versus gas) and one of the most common mistakes on any high-performance motor is to overdo the carburetion. Luckily the stock 240Z Hitachi SU is a great carb for both street and performance and automatically meters the gas depending on the airflow through it. So whether you are stock or have a cam with large duration, with the proper needle the SU carb tries to keep the correct mixture from idle to redline. A simple, accurate design.
See here for Weber DCOE tips and tricks.
The "good" SU's were from 1970-1972 and will have 4 or 3 screws holding down the domed piston depending on which year it was made. The year makes no difference for performance as the nozzles and needles from different years interchange. If you have carbs with the square choke flap in the inlet or round flat tops then you have poorly performing emission carbs. Exchange them for earlier SU models.
NOZZLES AND CARB NEEDLES
- the '70-71 240 used "N27" needles and related nozzles.
- the '72 manual trans car used N54 needles, the '72 automatic used N58, both with the same '72 nozzles.
- the '73 nozzles/needles were emissions designs, not recommended for performance.
- SM needles from British SUs are excellent for performance. See my Dyno page for details.
My own setup is .100 Z Therapy nozzles, SM needles on a set of 1970 carbs, 260Z "N36" intake.
SETTING SU FLOAT BOWL LEVELS
We've all spent afternoons syncing the carb airflow, topping up the damper oil and making sure the jet needle/fuel nozzle levels are set properly (2 1/2 turns down, etc). But how many of us have checked to make sure the gas float levels are identical on each carb? This is actually a very big deal. If the fuel levels are different in each float bowl, even a small bit, one carb will always be lean or rich compared to the other.
The issue is that the SU uses a combination of incoming gas and the float closing the fuel-valve to create a steady fuel level at the tip of each fuel nozzle. If this fuel level varies between carbs then its also at a different level on each jet needle.
HOW TO MEASURE FUEL LEVELS?
This has been covered in several places online. Be careful since you're dealing with gasoline(!) Mark the front of the float bowl 23mm down from the top edge of the bowl (not the top of the lid). These measurements are done with the carbs on the car.
- Get some small diameter clear plastic hose from the hardware store, cut a piece about 18" long.
- Connect one end to a float bowl's outlet and run the other end up over the carb. Some people connect the hose to the drain plug on the float bowl but the fuel hose outlet is a lot easier.
- Bring your fuel pressure to what it would be while idling. This means if you have a mechanical fuel pump turn the engine over a few times with the coil wire off. With an electric fuel pump just turn the ignition on to pump up the fuel pressure.
- The fuel level will equalize in the hose and should line up with the 23mm mark on the float bowl. By sighting the level in the hose and bending the tab on each float you can get the float fuel levels to match within a millimeter.
HOWEVER: Even though adjusting the floatbowl levels to 23mm down is a factory setting, it doesn't guarantee that the fuel levels in the carbs are the same.
I did some measuring with a straightedge and found that on my 4-screw SUs a 23mm fuel level in the float bowl corresponds to exactly 1 centimeter (10 millimeters) below the fuel nozzle "ledge" in the carb. But how do you see to measure fuel 1 centimeter down inside the fuel ozzle? See below.
- Remove the dome and main piston from each carb so you can look down the tip of both fuel nozzles.
- Screw each mixture nut exactly 10 turns down from fully up. Each full turn drops the nozzle tip 1 mm, so 10 turns puts the tip of the fuel nozzle 10 mm (1cm) down....which happens to be the 23mm float bowl level.
- Then look down the tip of each fuel nozzle and adjust each float to set the gas level at the fuel nozzle tip.
I ended up taking mine to 9 turns down and set the fuel at the meniscus of the tip. Then when I went to 10 turns the fuel was exactly at the tip. A bit of a juggling act but after a few minutes you will get the hang of it. When you get them to match it's a great feeling.
NOTE #1: if your mixture nut won't go down more than a few turns, it's because the factory "stopper" next to the nut is still in place. Unless originality is a concern, you can permenantly remove both stoppers from the bottom of the carb.
NOTE#2: if the fuel level is too high and overflows the nozzle tip, you will need to drain each float bowl a bit before starting again.
The result was a lower, more solid idle and less choke needed at startup. I get no stumbling off idle and part-throttle acceleration is smoother, acceleration more powerful. Cruising on the interstate requires a lighter touch on the accelerator. Interesting.
I recently bought a quality carb rebuild kit which contained pair of long/short valves for each carb (with no mention in the instructions). Different year SUs came with different length float "ears", but which length valve went with each year carb and why? The stock valve is labeled 1.7. My stock 1970 SU's did have a 2mm longer valve in the front and short one in the rear. But the valve lengths aren't mentioned in any of the Datsun manuals and when I spoke to several informed sources I got conflicting answers. Some people suggested I use short valves in both carbs but couldn't explain why. It surprised me on a 40 year old car that no one knew the answer to what must be a common question.
I finally spoke to the Z Doc in Roanoke Va who reminded me of the real reason: It's because of the direction that the float arm pivots between the front and rear carbs. Under acceleration gas flows away from the needle in the front carb but towards the needle in the rear carb. The factory must have determined a need to compensate for this, too bad they never shared it with us. Regardless of which ones you use, the more important issue is to make sure afterwards you get the fuel levels at the tip of each fuel nozzle as mentioned above.
Many people don't realize that mucg of the gasoline sold in the Northeast US and California is formulated differently than fuel in the rest of the country. While leaded fuel was phased out in 1996 in the United States, little is said about the widespead use of RFG (Reformulated Gasoline). RFG contains a high percentage of "oxygenates" which allow fuel to vaporize more quickly, especially in cold weather during engine warmup to reduce emissions.
Phase I RFG was mandated by the EPA in January 1995, and began appearing at gas stations in large metropolitan areas...which had higher air pollution. I remember the first time I filled up with RFG in Richmond, VA it had a peculiar acetone smell, different than the oily gasoline smell. One of the key oxygenates used then was MMT which is now illegal because it started showing up in water supplies and could be tasted in tap water(!). So ethanol is now the common additive, but it cannot be used higher than a 10% concentration or it doesn't burn properly.
Phase II RFG began in January 2000. RFG II was designed to produce even less emissions than RFG I. Rarely mentioned is that RFG contains less energy than "real" gas because of these oxygenates, hurting gas mileage by about 3%. This means less horsepower too. "Summer" and "Winter" RFG are rotated in and out of circulation starting about October (transitioning to Winter) and May (switching back to Summer). Summer RFG has the lowest amount of oxygenates and most "power" while the Winter gas has the most oxygenates and poorer performance because it vaporizes quickly. This means if you're running Winter RFG and suddenly get a warm day you can find your engine pinging, so don't dyno or race your car on Winter RFG.
Interestingly, RFG doesn't produce chocolate-tan spark plug deposits the old tune-up books have been showing for decades. Instead, plugs can tend to have a whiter appeance as though they are running lean which makes plug reading more difficult. I have also heard a rumor that RFG gas pings (detonates) very quietly compared to old gas which tended to sound like there were marbles in the cylinders. I push 10:1 compression with aggressive timing on my Z and never hear pinging which worries me I'm missing something. I don't want to push my engine into detonation to prove RFG pings silently...but I believe it to be true.
Click here for detailed info on RFG from the EPA. Also, here's an EPA map of the areas that use RFG. If you live outside these areas feel lucky that your car engine makes more power than the rest of us.
If you are using carburetors you can remove the stock mechanical fuel pump from the head to reduce drag from the cam and replace it with an electric pump. There are two types of aftermarket fuel pumps: Rotary Vane, and Oscillating. The square Purolator/Facet brand electric pumps found in auto stores are the oscillating type. Reliable I'm told, but the design is very noisy with a loud tapping that's audible through the rear deck, especially if you have a quiet exhaust. A rotary vane pump produces a quieter whirring sound and is the style used on newer cars.
My own rotary vane choice is the Carter CRT-P4070. It can produce 72 gallons per hour and 6psi max and is considered very reliable which was my goal. The perfect spot for it is just under the mustache bar against the brace that holds the differential. Pushing fuel through my stock 240Z fuel rail this pump produces about 8 psi at the carbs, while the factory pressure required of SU carbs is 3.5 psi. Even though it seemed to run fine I didn't like the mismatch so I have recently installed an adjustable Holley fuel pressure regulator between the pump and fuel rail to dial down the pressure to 5psi. With the extra fuel demand of a L28 I think the tiny extra bit of pressure will help keep the fuel supply up without overpowering the valve needles. I have to admit it's a satisfying feeling to dial in my own fuel pressure by using an allen wrench.
2011 NOTE: this pump appears to have been replaced by the GP-4070 which Carter calls a "competition series" pump. The specs and design appear identical to the CRT-P4070. Wonder what qualifies the GP-4070 as a competition pump and the P4070 not?
On 240's, you will have to cut about 2 inches of metal from the front/right edge where the shifter goes through the trans tunnel when using a 5-speed. Otherwise the throw into 5th gear will hit. This cutting is the price of a 5-speed trans and is not a big deal at all, the console covers it.
- There are 2 versions of flywheels on all '75-83 motors: coupe and 2+2/turbo. 23 lbs each.
- - Coupe and 2+2 clutches aren't interchangeable because the pressure plate dowel holes won't match the flywheel dowels.
- - A Zcar 5-speed will fit on any year Z block and any year L28 clutch can be used. But the throwout bearing "collar" must match the style of the flywheel (coupe or 2+2). In other words, if you have a 2+2 flywheel, you need to change the throwout collar to a 2+2 version. A coupe flywheel uses a coupe collar.
- - Automatic transmission engines have a 1/4" metal spacer between the driveplate and crankshaft, remove this when adding a flywheel.
- - A pilot bushing needs to be installed in the crankshaft if using an auto trans engine (they didn't get one).
- - Unless you need the accessories don't use a big 3-row harmonic balancer, get rid of it. I've read that taking 10lbs off a flywheel is the equivalent of taking 207lb off the front of the car. So I believe removing 5lbs from the front of the crankshaft is desirable too. Also, I've been told the 3-rows like to break up over 6,000rpm.
- - All L28 balancers have identical TDC timing marks and are interchangeable.
'75-79 280Z(X)s had a 3.54
'81-83 turbo ZX's had a 3.54
'81-83 non-turbo ZX's had a 3.90
the '85-86 200SX turbo had a 4.11
the '87-89 LSD was a 3.70
- If it's a 3.54 it will read "39:11"
- If it's a 3.70 it will read "37:10"
- If it's a 3.90 it will read "39:10"
- If it's a 4.11 it will read "37:9"
- Style 1 came on '75-78 cars. It came with 1 or 2 internal fat magnetic pickups inside.
This distributor uses a magnetic reluctor and pickup to send a strong pulse to the FI brain underdash which fires the coil. This is considered a "Magnetic Trigger" distributor.
- Style 2 came on '79-83 cars. It came with a built-in ignition module on the side
This uses a magnetic reluctor wheel and small pickup coil to send a pulse to the ignition module on the side of the distributor which fires the coil. A simple, self-contained ignition system. Pre-1981 models used the E12-80 module, '81-83 models used the E12-92.
- Style 3 came on '81-83 turbos. It uses the FI brain and a crank-firing system.
These require the turbo FI brain and several sensors, I doubt if it could be wired into an older Z without a lot of trouble.
- - Unplug and remove the voltage regulator on the right firewall.
- - On the regulator's rectangular connector coming from the wiring harness, look at the wires going into the bottom. Plug in a jumper to bridge the white wire and the yellow wire. It may appear that both wires are yellow (due to age). Luckily there are only two solid light-colored wires...these will be the white and yellow.
- - Plug the 2nd jumper between the black w/ white stripe, and the white w/ black stripe wire. Leave the other holes alone.
- - Reconnect the thick white/red stripe wire (Battery) to its spot on the alternator.
- - Reconnect the thick black wire (ground) to its spot (Earth) on the alternator. The "P" connector on the new alternator isn't used.
- IMPORTANT STEP: Go to Radio Shack and get a "1N5402" diode. This needs to be soldered inline with one of the wires on the plastic T connector that goes to the back of the alternator. If this step is missed, the engine won't turn off with the key(!) Make sure the "line" on the end of the diode faces the connector. Don't solder directly to the connector like my graphic shows...just solder it inline with that wire of course. Diodes are sensitive to heat so be careful not to overheat the leads when soldering.
- I have used the MSD Blaster-2 (.73 ohms), Crane PS-91(.43) and PS-92 (.20). I generally use a MSD Blaster 2 but like the simplicity of the E-core designs. I am currently using an Accel 14009 (.70) seen below.
- Use a K&N filter in the stock 240 air cleaner. This keeps all the PCV hoses and vacuum lines active, reduces intake noise and gas smell, and makes the engine bay look stock.
- My second choice would be the individual round K&N filters that use nuts to hold the filters on.
If you want to repaint your 240 air cleaner use "Chevrolet Orange" engine enamel. Available from the auto parts store. I don't know what the original color was 40 years ago but it looks factory to me.
FOURTH - the transmission
Borg-Warner T5 and lightened 240mm turbo flywheel
Datsun used three 5-speeds for U.S. Zcars
- One version from 1977-80
- One version from 1981-83
- A Borg-Warner T5 in 1983
My page on installing a Borg-Warner T5 in a 1st generation Z.
Nissan called the '77-80 trans a "wide ratio" while the '81-83 was called a "close ratio" 5-speed. The early one has the lowest 1st/2nd gears for acceleration, but a wide spread between 2nd and 3rd. The later one has a taller 1st/2nd but a tighter spread between 2nd and 3rd. It also has a much taller 5th for cruising. Your choice.
According to a Z Doc friend who rebuilds transmissions the early 5-speed is a 4-speed with 5th and reverse sharing the same fork. He said it's more common for people to "blow" 5th gear on the earlier style as the fork is weaker. He stated the later 5-speed is a genuine 5-speed which is stouter. I call the early one a 280a and the later a 280b to keep them straight.
Keeping the speedometer correct
Everyone gets confused about how to calibrate the speedometer after swapping differentials, it's actually very easy. The speedometer is metered by a plastic, toothed cog on the end of the speedometer cable that screws into the transmission. This cog is paired with the differential, not the trans. So it doesn't matter which trans you have, all you do is select the proper cog for the rear-end ratio you have in the car. While they are colored for easy identification, the Nissan dealer only has them in their parts list as "17, 18, 19, 20, or 21" tooth cogs.
|YELLOW is the 16 tooth for the 3.36
BLACK is the 17 tooth for the 3.54
BLUE is the 18 tooth for the 3.70
WHITE is the 19 tooth for the 3.90
RED is the 20 tooth for the 4.11
PURPLE is the 21 tooth for the 4.38
~When in doubt, count the number of teeth~
NOTE: There are 2 different aluminum cog "sleeves", a '75-80, and '81-83 with different cog "offsets". If you look closely in the picture above notice how the red cog is offset slightly to the right, and the blue to the left. This means you must keep the sleeve with the transmission it came in, and only swap the cog. Otherwise the cog may not mesh the proper way inside the trans.
FIFTH - the flywheel and clutch
This is a 2+2 flywheel and clutch
Measure the diameter of your clutch disc.
-If it's 225mm wide then you have a coupe version which uses a 550lb pressure-plate.
- If it's 240mm wide then you have a 2+2/turbo version with a 780lb plate and a wider disc.
- Flywheels are identical in diameter and weight at 23 lbs (only the contact area is wider).
Unless you're racing you can usually get by with an OEM style clutch because the 240Z is so light...I have been autocrossing and dragracing for years with an OEM with no issues. But this year when I added my triple Webers the clutch began to slip when the engine hit its torque peak. I decided it was time to upgrade and installed a standard Centerforce II. The Centerforce fits perfectly and will actually chirp into 3rd gear on shifting. Pedal feel is excellent and engages smoothly.
Over the decades the hole bored in the clutch pedal that holds the clevis pin gets worn oval, the pin gets scored too. This adds slop to the pedal and makes adjusting it a chore…as the settings always seem to drift. To fix mine I removed the pedal, drilled out the clevis hole slightly and welded in a steel bushing from my hardware store. Into that I tapped a slightly smaller bronze bushing and ran a drill bit through to make the ID the size of the clevis pin. The result is a strong bushing with a replaceable bronze core…and a nice smooth action that will not wear the clevis pin. BTW, don’t try epoxying the bushing in or using a super-bond glue, it will crack and fall out…happened to me twice before I went the welding route.
IMPORTANT TIP: Frequently forgotten is that there is a short, heavy return spring on your clutch pedal that connects from the clevis arm to a bracket underdash. This spring is responsible for pulling the pedal back and holding it firmly against the rubber stop to provide a zero reference point for the clutch. If you have lost your spring over the years…your clutch pedal is essentially swinging free…adjusting the clevis rod in and out will seem to have little effect. You may be able to sneak by without the spring if you have a stock clutch but if you install a high performance version you will have trouble adjusting it properly. I think this is a chief cause of trouble when people install a Centerforce or similar. The pedal spring is Nissan part number 46587-N4401.
ZOOM/Perfection brand STAGE 1,2,3,4
Light flywheels have been used for decades in racing to reduce drag on the engine and to make it spin up faster. It won't make the engine develop more horsepower internally but can cut down on parasitic drag and give you that quick Indy-car revving sound. Better for track racing than dragracing as on smaller engines the rotational inertia that helps the car off the line is reduced. This loss of inertia can make it harder to modulate off the line and some people consider the the lightest ones (about 10lbs) more difficult to drive in traffic. On motorcycles having a too-light flywheel can make it stall between shifts(!)
On my L28 I am using a stock coupe flywheel custom-lightened to about 16 lbs. It speeds up my revving by about 25%, and makes the engine much snappier without losing driveability. I have to be careful at stoplights on hills as the engine revs up much faster than expected when I need to move forward. With a loud exhaust it raises a few eyebrows.
SIXTH - the differentials
4.11 from 200SX turbo, freshly painted
There were three different Zcar R-200 ratios from 1975-83, none were limited slip until 1987. 280ZX automatic transmission cars came with an R180, so if you want to find a R200 3.90 look for a 1981-83 5-speed coupe in the junkyard. Don't try to analyze the confusing table in the Haynes manual, this is the easy way to do it:
If you want performance get the 3.90 R200 out of a 1981-83 5-speed, NON-turbo ZX. If you're speed freak like me use the 4.11 out of the 200SX turbo. While not a limited slip, the 4.11 adds more snap over the 3.90 and can make your Z a real rocket off the line. Zcar R200 halfshafts snap right in to the 4:11.
BTW: to get R200 halfshafts out, I find the easist method it to unbolt the wheel end and "yank" the halfshaft hard a few times. A little circlip in the diff holds it but it will (usually) pop right out, the yanks don't hurt it. To get them back in you can lock it in place by thumping the end with a mallet which locks it.
GEAR OIL REFILLING TIP: Instead of uninstalling the differential I remove one halfshaft and add the oil though the side of the case.
LIMITED SLIP DIFFERENTIALS
Despite the performance of the Z, Nissan only made a limited slip diff very late in the Z's life. They made 2 types: a standard LSD and a LSD with a viscous internal drive. The 1987-89 Turbo 300ZX's had the "good" 3.70 LSD, and can be identified by it's finned rear cover. This cover needs to be replaced with the smooth R200 cover to fit properly to the 280Z mustache bar and the front driveshaft flange needs to be replaced with the one your driveshaft uses. The '88 white SE 300ZX came with the "viscous-drive" R200, and can be identified by a sticker on the driver-side of the diff that says "VISCOUS LSD". While the viscous model fits into an earlier Z, R200 halfshafts don't lock into them without some fabrication of new halfshaft fittings.
TO DETERMINE THE RATIO (internally)
If you're not sure which ratio R200 you have lying around the garage, check it this way: Remove the rear plate (drain the oil of course). Then rotate the large ring gear until you see these numbers stamped into the edge facing you.
The first number marks the number of teeth on the large ring gear, the smaller is the number of teeth on the pinion gear connected to the driveshaft. Can you swap ring and pinions around to create the ratio of your choice? I checked with my buddy the Z Doc, and he said it's difficult to get the preload and tooth geometry setup properly (he tried it). Oh well.
HOWEVER: Since the 3.70 and 3.90 apparently use the same 10 tooth pinion, I wonder if a 3.90 ring could be swapped onto a factory limited-slip assembly? This would make a "factory" 3.90 limited slip!
There is more to the Zcar ignition system than any other part of the car, so this is a long section below.
POINTS vs ELECTRONIC IGNITION
Points distributors are an obsolete technology when it comes to high performance engines. The reason is that Dwell (the amount of time the points stay open) changes if there is any play in the distributor shaft. Dwell directly affects ignition timing, so any slight rocking back and forth of the shaft varies your ignition timing. Point float and bounce can also cause the spark timing to scatter at high revs. Datsun competition makes a solid advance plate breaker to address this. Mallory also makes an interesting dual point distributor for Datsuns which I have never tested.
Electronic distributors are usually rock-solid when it comes to timing. Shaft play can still cause slop in the distributor but generally doesn't cause the timing to fluctuate the same way. An electronic distributor can give you full coil saturation with a strong, accurate spark past redline.
Nissan made three electronic ZCAR distributors
WIRING A E12-80 and 280ZX DISTRIBUTOR INTO A 240Z
This mod converts a 240Z to an ZX electronic distributor. It's not needed on a 280Z or ZX which already have electronic ignitions.
- Find a 1979-1983 280ZX distributor. If its '81-83 it will have the E12-92 module which needs to be changed to a E12-80.
- Remove and clean the metal rear of the IC module so it can ground itself to the side of the distributor.
- Remove the triangular hold-down plate on the base of the distributor. Burnish it, as well as the spot where it contacts the distributor and replace...this helps everything ground well to the block. Note that this plate rotates, you may need to play with the position to get the proper timing mark range you want.
- Use quality spade lugs and wire with TIGHT crimps and solder the wire to the spade connections. Don't solder or crimp onto the E12-80, just make sure the spades fit on tight.
- You will need to buy a longer L28 distributor base for the front cover if this is a 240Z. Motorsport Auto used to carry them them.
A 240 tach will not work with this setup because its inductive pickup isn't compatible with the signal from the E12-80. There are two solutions: Replace it with a 1975-78 280Z tach and connect the tach sensor lug to the negative terminal on the E12-80 module. If the tach jumps around, solder a 7500-10,000 ohm resistor inline with the sensor wire to reduce the signal voltage. If it still won't work simply buy a Autometer #3990 black face tach.
WARNING: if you have a MSD type igniton DON'T hookup the E12-80 or tach directly to the coil. The 450 volts can fry it. Follow the ignition's hookup guide.
Old news, but the teeny 40 ampere alternator and mechanical voltage regulator that came in the 240Z are marginal, especially when using an electronic ignition system. If you're not an electrical guru here's the basic explanation:
CURRENT is the amount of voltage 'draw' that your electrical system pulls from the battery or alternator. Every electrical item from your gauges, to dashlights, to the ignition, draws this current rated in amperes (amps). The manufacturer simply adds up the total amperage that electrical items in the car use and installs an alternator with enough current to supply everything. If everything in the car draws 30 amps total, you would likely get a 40 amp alternator.
In the early 1970's a stock 240Z only needed an AM radio, points ignition, basic lights and was given a tiny 40 amp alternator. But today you add an MSD type ignition, a big car stereo amp and flamethrower headlights, and you easily pull much more current than the stock alternator can supply. In addition the Voltage Regulator on the firewall is a "mechanical" type with points inside that open and close just like on an old distributor. These m echanical regulators have been obsolete for 30+ years...Nissan went to internally regulated alternators in the late 1970s.
I realized I needed an upgrade on my 240 when my ammeter needle would jitter at idle. Even more obvious was that at night my dash lights would dim when I neared redline. After spending hours checking grounds and cleaning connectors, I finally decided to get rid of my vintage setup. Instead of a monster aftermarket alternator that puts out 120 amps I took the factory route and used a Nissan 1981-'83 non turbo 280ZX alternator which is a 60 amp version.
THE ALTERNATOR MOD FOR 240Zs only:
Buy a new "1981-83 Nissan 280ZX non-turbo" alternator at the auto store. Replace the original alternator and follow the directions below. Before you start, fabricate two little wire "jumpers" (cut a wire about 3 inches long, strip the ends, and solder/crimp a male spade on each end.
COMMENTS: On startup I found my exhaust note is smoother at idle and idle is rock solid. I suspect the more stable voltage at idle enhances the MSD ignition. On the road the engine feels smoother with none of the hiccups I was getting when lugging the engine to low revs or accelerating in too low a gear. Revving past redline is more smooth and solid with a bulletproof feel. My ammeter is solid and accurate and my dash lights are brighter and wipers are faster. I measured 14.58 volts at the battery...just what it should be. I'm not saying this makes the car faster, but it's more driveable now without the voltage sagging at idle and redline like before. This is probably the easiest and most worthwhile of all the 240Z mods. I would save your old 240 alternator/regulator for an emergency, or to swap back to stock someday.
NOTE: your dash ammeter will not work after this upgrade. The solution is to replace the ammeter with a 280Z gauge that shows volts, or an aftermarket gauge. If it doesn't matter to you just ignore the old ammeter.
NOTE: You will need to come up with a way to shield the connector and jumpers from the elements. You could clip the connector from the old regulator to make a plug-in jumper arrangement which would look cleaner than just using two jumpers.
MSD STYLE IGNITIONS
There are several companies battling out on who has the best ignition. Most use the same concept: provide a multiple spark out to 3,000 and then revert to a single hot spark to redline. So the brand choice is up to you. I'm currently using an MSD 6A on my carbureted F54 triggered by a E12-80 on a ZX distributor.
I spent some time on the interstate with a stopwatch doing 60-80 and 70-90 runs in the top three gears, comparing a E12-80 firing a MSD 6A, and a E12-80 module by itself. The times were within a tick of each other, back and forth. Kind of inconclusive. The MSD/Crane DO give smoother idle, need less choke, drive better when cold, and cut down on my exhaust smell at idle. But despite all these credentials I'm not convinced they actually makes the car faster over a E12-80 alone. I've decided that on a carbureted motor the better starting and idle quality alone are worth using a MSD-style ignition, even if I'm not sure the top end is better.
I haven't used a Pertronix setup but a friend has one on his '71. It seems to work perfectly and I'm impressed at it's simplicity and quality. A great option if you can't locate a L28 electronic distributor, it uses an optical pickup to replace the factory points. I would still pair it with a MSD ignition to boost the spark. Make sure to lube up your breaker plate and check the operation of the vacuum advance weights and dashpot while you're in there.
CHEVY HEI MOD
Using a GM HEI module is a 25 year old way to put a 1975-78 280Z distributor on a 240. The problem is that the GM HEI was designed for the low redline of a V8 and is well-known for it's poor spark saturation abilities above 4,500rpm, even Chevy people hate them. I've heard of people adding a HEI chip onto their 280Z or ZX ignition which makes no sense. Why would you add a HEI chip on top of the existing electronic ignition setup?
Even on it's own I consider the HEI a poor mod for performance and I don't recommend it: Back in 1996 I used a 1977 280Z distributor and HEI on a SU carb L28 I had built. It pinged easily for some reason and I was never sure exactly why, so I quickly I converted over to a 280ZX distributor with a E12-80 which solved the problem. The E12-80 sells for $200, the HEI module for $20, you be the judge.
Every performance part on the market advertises performance numbers and feature/benefit results to help you decide what model to buy...except one: the Ignition Coil. Coil manufacturers advertise them as having a "hotter spark" or "45,000 volts" but say little about how to choose a coil for different engines and driving styles. That they market their products towards the drag and circle track racers while ignoring the classic/autocross/rally market is very puzzling to me.
Coil manufacturers do publish primary/secondary resistance, output voltage, spark duration/current, but they never actually tell you how to interpret them. Is it OK to use a racing coil on the street? What happens if you use the wrong coil with a racing ignition? Which is more important: higher spark duration or current? So I posed these questions on a respected manufacturer's ignition forum hoping to receive some wisdom. Their response was "Our xxx model should fit your car just fine". Gee thanks.
Cyncial minds might conclude that because it acts as "gateway" to boost the spark from the ignition that you have either a high performance coil or a stock one, that minor spec differences don't matter. If I were a manufacturer I would remove the hocus-pocus and plainly state which measurements affect real world performance and horsepower. Has a racing or hot rod mazagine ever tested different coil models on the same engine to see if there's a difference?
- A coil is simply a transformer that steps up 12 volts to several thousand. Its positive terminal gets a constant 12 volts to power it on, and a pulse to the negative terminal causes the secondary windings to produce a large spark out of the center tower. This is the common setup on just about every car over the last 100 years.
- A capacitive discharge ignition like the MSD sends 450+ volts to the coil (instead of 12). This is why a better ignition produces such a mammoth spark out of the coil.
- Serious racing coils have very low resistance "primaries" (primary windings) which draw a larger amount of current than the higher resistance versions. This is why real racing coils are advertised to only run with a companion racing ignition: if you run one on a stock ignition the coil can draw too much current from the ignition and damage it.
- True racing coils run hot and can burn out after "extended periods of use". This means that normal street driving is hard on them since they are designed for short track races and dragstrip runs.
- There are many performance coils out there but some designs haven't kept pace with technology. Look in the online catalogs and you see several generic oil-filled "performance" coils. I consider these iffy as they were designed for stock engines or muscle cars with points, not 10,000 rpm racing ignitions. I doubt they have changed internally since the 1970-'80s.
I would recommend getting rid of your old 240Z tach if your focus is on performance. Vintage looking but not designed well, they're not very accurate even when working well and start jumping around as they age. I'm not into the white face look, I replaced mine with an Autometer #3990.
Surprisingly, stock coils on older 12V points systems on cars were designed to operate with a max of 6-8 volts. The reason is that on points distributors the entire voltage from the coil passes through the points, and too much voltage would burn them out. So a ballast resistor was put inline with the 12+ wire to the coil to limit the voltage the coil produces.
When you turn the key to start, the ballast is bypassed, and the coil gets a full 12V to put out a hotter spark for starting. Releasing the key inserts the resistor back into the circuit to preserve the life of the points. Why not design the ignition to use 12V all the time? Well, nowadays they do but before 1975 or so that's the way points ignitions were designed. This means if you buy a high performance coil and simply install it, the ballast resistor may limit the new coil's power output. On a points distributor you can connect a wire across the ballast, it will route a full 12-14v to the coil and pick up some voltage, but it can shorten the life of the points.
NKG plugs are the best I've used in a Z engine...smooth, predictable and long lasting. Bosch plugs are fine on German ignitions but many consider them less than satisfactory on Z motors. I've been told that German ignitions evolved with a different overall resistance from coil to plug than Japanese ones which causes a mismatch. For whatever reason, some Z owners report misfiring and poorer performance from Bosch. There's a big markup on "platinum" plugs too...companies know that people think products with "gold, platinum, silver, diamond" in the name are better. Centuries-old marketing, heh..
I think the best Z plug to use on an electronic ignition is the NKG BPR6ES-11.
A few years ago Grassroot Motorsport magazine recommended the NGK ZFR6F-11 sparkplug for Z engines. It's a "V-Power" plug with a projected tip which extends out into the center of the chamber simulating advancing the timing slightly by firing the mixture faster. Projected tips provide a more complete burn through the rev range, creating "free horsepower" and improving throttle response. Be careful using extended tip plugs in a shaved head or you might touch the piston(!)
Also, be wary using multi-electrode plugs, especially on high compression motors. I spoke to a NGK tech once, who said that the nooks and crannies on multi plugs can create lots of little hotspots and contribute to pinging. He said that multis are mainly designed for the modern hemi-style chambers on Hondas where the mixture is quenched in from all directions.
My 2 CENTS: Don't waste your time on plugs that use hocus-pocus: use the plugs the factory chose. If you want to increase spark performance spend your money on upgrading the ignition system instead.
PERFORMANCE PLUG GAP
The proper gap on a high performnance engine is another question that the ignition companies won't answer completely. To be fair, there are a lot of engines and driving conditions to take into account. But as a general rule on a stock engine you can't open the plug gap much more than recommended by the factory because the stock coil will produce a weaker spark.
However, if you are running an aftermarket MSD type racing ignition they are designed to produce a very powerful spark and can "take advantage" of a wider plug gap. What does this mean? It means you can widen the gap by about .003-.005 from stock because the ignition can still produce a strong spark across the wider gap. This longer duration spark is said to give more complete combustion and maybe more power. Drag Racing lore is to open the plug gap to .050 (or wider). But on high compression motors today's wisdom is to keep it at about .045, because as compression goes up such as on turbo and supercharged motors it's harder for the spark kernel to start. If you open a plug too wide the extra resistance at the plug electrode can actually cause arcing in the distributor cap and supposedly even from the plug electrode to the piston top in some cases(!)
The stock 280Z/ZX gap is .038-.043 so on my carbureted L28 with 280ZX distributor and MSD 6A I have experimented with .045 and .050 plug gaps. Using .045 feels very correct to me and the engine has a very predictable and satisfying feel. Opening it up to .050 makes acceleration feel smoother and somehow...different, kind of hard to explain. I don't have a good reason but my gut likes .045 better, it just feels better to me somehow.
I really like 8mm Magnecor competition wires. Very high quality blue silicone, they are "real" competition wires and put the other designs I've seen to shame. Grassroots Motorsports Magazine did a test a few years ago and found that these wires added 1.5hp to a stock BMW motor(!) But despite what people think, performance wires don't actually "increase" horsepower. They simply work transparently to allow the coil's full output to reach the plugs consistently. These certainly do, with very clean output all the way past redline, they even smoothed out my idle. Nice.
Dielectric (d-lktrk) noun.
A nonconductor of electricity, especially a substance with electrical conductivity of less than a millionth (10-6) of a siemens.
Dielectric grease does not conduct electricity. It's purpose is to protect the surfaces of metal conductors from corrosion, sealing spark plug boots to keep water from getting in, as well as preventing arcing. Putting it on metal connections like distributor cap terminals, rotor tips, or injector contacts can disrupt signal transfer. Personally I think the companies deliberately call it "Tune-up grease" so people will slather it on at tune-up time thinking it's some sort of metal cleaner.
To clean old connectors I like to use a quality contact cleaner/solvent to blast them clean, then use an exacto knife or sandpaper to scrape any oxidation off. Standard brake cleaner spray is a good solvent but on electrical connections you want to leave a thin film of protectant on the metal to keep it from re-oxidizing. Years ago the high-end magazine "AUDIO" recommended WD40 as a high quality lubricating oil for cleaning and lubricating the volume controls on high-end preamps. So I use WD40 to protect conenctions. Places to clean are the voltage regulator connections, wiper motor plug, injection brain connector and injectors. Also open the injection airbox and spray the circuit board to clean the resistive wiper. Check the little ground connector that screws into the lower shock tower just below the battery on 240s...it sticks out of the wiring harness on the frame rail.
MECHANICAL ADVANCE CURVE
There appear to have been two different distributor choices on '81-83 L28s. If you take off the breaker plate you can see "8.5" or "9" stamped into the top of the advance weights. 8.5 came on the manual transmission cars, 9 came on the automatic cars. Double these to get the total mechanical advance for the distributor (17 or 18 degrees). Published specs show the mechanical advance coming in fully at 2800rpm on the 8.5 degree and 2700 on the 9 degree models. The vacuum advance is listed as adding 15 degrees. This means that a stock '81-83 distributor gives you 17-18 total mechanical with 15 degrees vacuum on top of that.
One mistake people make is bumping the static (idle) timing up to push the mechanical advance closer to 34-36 degrees BTDC which is considered the region for performance. You have to be careful because if you have the static timing bumped up too far, when the vacuum advance kicks in at part throttle it can throw the max timing way into the 40s: heavy pinging and damage to the rings can result. Another problem is that after 30 years the advance springs may be stretched or the weights gummed up. So you may not be getting full advance, or it may be coming in too early.
I recommend getting your distributor rebuilt by Advanced Distributors. They know the secrets of enhancing advance curves on imports and can recurve yours for performance. They have done quality work for me.
For the vacuum advance dashpot to work properly it needs to be connected to a "manifold vacuum" inlet as opposed to a "port vacuum" type. Manifold vacuum is what the brake booster uses,this is the intake area between the carb butterflies and the intake valves in a cylinder head. Port vacuum is "outside" the intake manifold and is a port usually inside the throat of one of the carbs. Port vacuum is very old fashioned, manifold vacuum is what Datsun engines use.
The vacuum advance dashpot's purpose is to react to vacuum from the intake manifold to move the breaker plate inside the distributor to keep the timing "optimum". It adds its advance on top of the amount the mechanical advance produces. Unfortunately, after 25 years, many dashpots are leaking, causing no advance and a big vacuum leak into the intake manifold.
Test yours by sucking hard on the hose going into the dashpot. With the distributor cap off watch the vacuum arm pull in. If you "hold" the pressure, the arm should stay fully retracted. If it slowly leaks down, the vacuum dashpot is leaking...and it should be replaced (it can't be fixed). If it's leaking so much you can hear your breath hissing then you have been leaking air back into the intake manifold which is not good. To fix the leak temporarily plug the dashpot hose end going INTO the manifold. It's better to run without vacuum advance than to lean out the motor and burn a valve.
TO DISABLE VACUUM ADVANCE Not running vacuum advance can make part throttle acceleration a bit sluggish and hurt gas mileage. To disable it simply remove the hose from the vacuum dashpot and plug the hose that feeds into the intake manifold. Using vacuum advance makes the engine drive better in my opinion though and I see no reason to disable it on the street. But vacuum advance doesn't do much under full-throttle so if you only drag-race or track race vacuum advance isn't truly needed.
MY OWN SETTINGS?
I use a 1981-83 manual-trans 8.5 (17) degree distributor, with the earlier E12-80 module on the side to fire my MSD 6A. I have had it recurved and advance my distributor timing to 12-14btdc. After lots of swaps and testing I believe this is the best setup for a L28 with flattop pistons.
stock cam in 1996
A race cam by itself won't add 50 horsepower to a Z engine. But by properly choosing one that takes into account your engine compression, fuel supply, and driving style it can really enhance the power and characteristics of the motor. It's difficult to resist buying a stage hotter than you need...especially if you want to make your car sound like a BRE racer. But the reason you shouldn't go too hot is that adding a race cam to a stock engine will reduce power...it reduces cylinder pressure and tends to move the power range too high for street use. I once knew a guy with a 5.0 Mustang who installed a very hot cam in his street car. The car accelerated like the handbrake was on until he got to 4,000rpm and then started pulling harder. He was convinced the car was fast but likely lost a lot of drag races. So choose carefully. Think of a cam as a tone control rather than a volume knob.
Duration is the amount of time the lobe holds the valve open. Hence, a large duration cam lets lots of air/fuel in and out at high revs but tends to lose some bottom-end torque. On the other hand a small duration cam adds power and torque at low revs by keeping air velocity high, but chokes off power at the high-end. Cams are typically sold as "Stage 1,2,3, etc" with each stage usually increasing the duration by 10 degrees, moving the power up the band by about 500rpm each time. Always compare cams using the @.050 figure instead of the "Advertised" duration.
Unless a cam is marketed as being ground on a new billet you should assume that it has been remachined (reground) from a stock cam. A regrind is perfectly fine but the smaller lobe base circles will require thicker lash pads be used. Thicker lash pads require you spend extra care measuring the rocker arm geometry to get the wipe patterns correct. I'm too impatient and prefer a plain old "drop-in" cam. There are several cams brands out there, check out the Z forums for testimonials.
COMMENT: My feeling is that about 270 advertised degrees (230@.050") of duration is right for street/autocross situations. Datsun race cams from the 1970's would run durations over 300° but those are intended for constant high rpm driving in race prepared motors, not normal street driving.
Stock factory Datsun cams are stamped "Japan" and are made of some very tough metal, lasting 200,000+ miles with no problems. But blank Datsun cam billets have been unavailable in the Nissan Motorsports catalog for over 10 years. As far as I know no one makes new Zcar cam billets anymore except the company "CWC". CWC Textron out of Michigan is listed as the "industry leader in ductile iron cams for passenger car and light truck applications".
Years ago my friend the Z Doc in VA. noticed that aftermarket ZCAR cams made with "CWC" billets were more prone to lobe failure when used with heavy performance springs. However, I have been running a nitrided cam made on a CWC billet for several years with no problems, I believe low ZDDP in motor oil is the main cause of cam failure.
So don't avoid a cam because it's made on a CWC billet...since it's the the only new billet choice out there we have no choice. The trick is to maximize its longevity. See my Lubrication section below for tips.
SINGLE PATTERN vs DUAL PATTERN CAMS
This is when the duration is the same between intake/exhaust lobes...or spread out (example: 260/260 vs 260/270). The concept behind a dual-pattern cam is if the exhaust valve has a larger duration than the intake it will breathe better into a restrictive exhaust system and produce more torque. If you use a freeflow exhaust system the effect of a dual profile isn't considered as important though. Performance turbo cams on the other hand can be just the opposite because of the different characteristics of the exhaust flow. As an example one turbo cam I've seen is 270/262 which appears "backwards" but is correct.
I've used two dual duration cams: Crane 262/272 (222/232@.050) and 272/282 (232/242@.050) the smaller one had better torque than the stage 2. My current cam is a 268/268 duration (230/230@.050") which has excellent torque.
Crane Cams used to make some great L-series performance cams. They were unique in that the lobe base-circle dimensions were identical to the stock cam. And with .450 lift they were simple drop-ins that could use stock lash pads and springs. All you needed were new rocker arms...perfect. In 1996 I bought a 262/272 duration cam (#168-0010) directly from Crane for $118, and a 272/282 (#168-0012) for $202 in 2000. But by 2003 they decided Z cams were "special grinds" and the prices went up to $300ea. Finally, in May 2005, Crane told me via email that they could no longer obtain the blank steel cam billets from Nissan and were dropping ZCAR cams from their catalog after many years of production.
While Crane stopped making Z cams in 2005, in 20101 their website read: S&S Cycle of Viola, Wisconsin acquired certain assets of Crane Cams, Inc. on May 7, 2009. Those assets include the inventory, intellectual property, and trademarks for all Crane automotive and motorcycle electronic and valve train products. The intellectual property portion includes designs, drawings, and cam profiles.
With the current economy I suspect Crane's Datsun Z cams won't be coming back, kind of sad that a decent performance part supplier is now likely gone forever.
Webcamshafts of Riverside, California is worth checking out. They have 50 years experience with creating custom and antique engine grinds as well as a couple of decades of producing Zcar cams. And after talking to them on phone they appear to really know their stuff. It turns out they use CWC billets for their new Z cams and also create reginds (your choice), but they "Nitride" them which involves heating them to 900 degrees and in an ammonia gas chamber. Nitriding creates a super hard lobe surface and is considered to increase the life of a cam 10-fold.
Unlike V8s you really don't need a radical cam to wake up a Z motor. So I resisted the temptation to go with their stage 2 cam the "# 91" which has 238/238@.050 duration. Instead I decided to order their "# 94a" grind with .430 lift, 230/230@.050" duration which they said uses stock base circles(!) Even though its their stage 1, compared to other brands it's at stage 2 level so I decided it was worth checking out. So later when I opened my mailbox I found a nitrided, higher duration, new CWC billet cam with stock base lobe circles. I installed it in my P90 head in mid October 2005 I found the wipe patterns on the rocker arms were perfect. NOTE: If you go with their #91 or higher grinds I'm not sure if they can retain the stock base circles. Talk with them before you buy to verify what you want.
MILESTONE: It is now May 2011 and my 94a cam is still going strong with no wear problems after more than 6 years. In 2007 I even replaced all the valves with stainless SI versions while keeping the old rocker arms which hasn't fazed it. Not bad.
PERFORMANCE: Despite its moderate specs on paper, the 94a isn't a baby cam. The exhaust note is deeper than stock with a nice cam burble. Acceleration is strong and linear down low and when you tach it out the acceleration is strong and it pulls hard all the way to 6800rpm. It doesn't have that "dead below 3k" feeling of some higher duration cams and is surprisingly torquey. I would pair it with a higher ratio rear end like the factory 3.90 to really enhance bottom end torque.
SPRINGS AND VALVE FLOAT
Valve float is when the valve spring can't control the valve at high revs and the valve flutters on the seat. This makes the engine misfire and lose power of course. It became an issue years ago when American V8 engines came with poor valve springs from the factory and would float the valves at ridiculously low revs. So drag racers started installing heavy valve springs to try and control the valvetrain at high revs. But I've never heard of or experienced valve float on any Z motor with stock springs, they were that good from the factory. However, if you are rebuilding a cylinder head I would replace your 25+ year old stock springs as it's a good time to do it.
The redline on a 240Z is 7,000, the 280Z is 6,400. This has nothing to do with the springs however. The valve springs were identical from 1970-83 and a properly tuned 2.8 liter motor can easily rev above 7,000. The redline differences between motors were because the larger an engine's displacement, the lower the usable power range. V8s can be a low 5,000 while a motorcycle might be 12,000 or higher.
You've heard this before, but when replacing the cam you should always replace the rocker arms. Everyone always wants to save a couple of bucks here, but you CAN'T. Even though the arms' surfaces might look smooth, they all have a subtle wear pattern that's mated to it's respective lobe. This mating takes place in the first few minutes of new cam/engine startup, and creates a perfect meshing between the two. If you use old arms with a new cam, the subtle wear pattern in the pad surface will wear into the cam lobes and damage them. This probably the most misunderstood part on a Z motor, unfortunately one of the more expensive too.
ROCKER ARM BRANDS
I broke in a new cam ten years ago using the now discontinued Crane Cams rocker arms. Several months later the engine started missing. On investigating, several of my cam lobe tips were actually worn down(!) They were broken in properly and had used what I thought was a quality oil so this was a shocker. In looking at the rockers, the metal on the pad surfaces was porous and veined, and looked like cast pot metal. A Crane tech told me one the phone that the porous metal was "normal' and that it was a specially chosen composition to work with the cams. ...hmmmm. I only got 5,000 miles out of them.
And in comparing the other non-Nissan rocker arms, I noticed that the Sealed Power and Melling brand used the same pad metal. Just speculating, but I suspect that Federal Mogul/Sealed Power wholesale their rocker arms to everyone, who repackage them under their own brand name. The real Nissan brand rocker arms are unique, lighter, ultra-high quality forged rocker arms with shiny steel pads...likely the reason why Nissan cams can pass 200k miles with no problems. Expensive, but worth it.
Motorsport Auto sells real Nissan arms for much less than Nissan or Beck Arnley. I installed a set and they broke in perfectly. Please keep em' in stock Motorsport........!! In 2005 I broke in a new cam with reground rocker arms from Delta Cams of Washington. They have two methods: you can order pot luck rockers from them or send in your own to be refinished. Personally I sent in my own to be refinished...that way I know their history and that they were all matched. They grind off as little as possible and for about $50 is a genuine deal.
NINTH - Lubrication
The quality of the oils used in the 1970's-80's was horrible compared to today. The old oils sludged up, burned, and turned to varnish over time. I remember a mechanic telling me he knew when a car used Quaker State oil by the amount of gunk in the bottom of the oil pan. That's why the "in-thing" back then was to change your oil every 2,500 miles, otherwise it dirtied up the motor.
Well, motor oils in the past 25 years have come a LONG way, even more in the past decade because of the demands of turbos and exotic high-revving motors. The secret of oil quality has to do with the API rating. The first letter (S) means the oil is rated for a gasoline engine. The higher the second letter, the higher the levels of detergent, varnish inhibitors, viscosity improvers in the oil. The old ratings from the 1970's (SA, SB, SC, SD) are obsolete, while today the current ratings are SM. That's why today an engine with 50,000 miles will be nearly clean inside, while motors from the '70s have a brown film baked on everything.
So changing your oil every couple of months isn't as critical as it used to be. The filter catches the dirt the same as it's always done, but the oil maintains it's slipperiness (viscosity) for well beyond 5,000+ miles now. The oil change Lube shops are having problems as a result. They still tell people to change oil every 3,000, while new cars manufacturers are saying 5-10,000. Times change.
Despite what your old manual says, don't use 10W-40, no new engine today uses it. Instead, use 10W-30. Because it's lighter, it will free up a couple of horsepower, rev faster, and will reach all bearing surfaces more quickly. I wouldn't use 5W-30 or 0W-30, I think those are too thin for Z motors. And don't use 20W-50, that stuff is like molasses and is meant for motors with large bearing clearances.
A single weight oil (ex: 30W) remains the same viscosity in all temperatures, while multis (ex: 10W-30) change with temperature. Singles are identical in quality (SL/SM rated) to multi-weights, but people tend to overlook them in the store. They aren't good in low temperatures though because they thicken. Hence the creation of multi-viscosity oils.
I've read that Porsche used to recommend only single weight oils in their 911 engines into the 1970's, and Crane use to recommend only a "single-weight Pennsylvania crude" to break in their new cams. Engine lore on motorcycles is to use single weight to break in a motor...this creates constant friction at all temperatures for balanced break-in. I used to use "Heavy Duty Castrol 30W" for rebuilt engine startup break in. But now that ZDDP in oil is at such low levels I don't think that's such a wise idea. If you are driving a Z with a L-series engine in 2011 you may want to take a look at Valvoline VR1 10W-30 below.
Older engines with mechanical valve tappets like the ZCar L-series engines and V8s with flat tappets (not roller cams) were designed for motor oil which contains a moderate amount of zinc and phosphorus known as ZDDP (zinc diaklydithiophosphate). ZDDP is considered a miracle lubricant for engines and has been used for about 60 years in motor oil and greases worldwide. Modern engines weren't designed to need ZDDP so the modern-day automotive world doesn't even speak of it. But for vintage car and hot-rod owners the diminishing levels ZDDP in oil is a real issue because it's required to lubricate the cam lobes and prevent wear across the rocker arm surfaces.
WHY IT'S VANISHING IN OIL
While zinc is not directly harmful to the environment, if its burned due to ring blowby it ruins your catalytic converter. So over last decade the EPA has pressured the oil companies to reduce the percentage of ZDDP in their passenger car oils. This extends the life of converters...which in turn reduces total car emissions. Pressure from the construction industry allowed some diesel oils like Rotella T made by Shell to use higher levels of ZDDP which they claimed was needed on heavy equipment. However, I don't like the idea of using bulldozer oil in my 7,000 rpm L28, even if it does have more zinc. Starting in 2007 construction equipment began receiving tighter emissions standards so zinc in Rotella is likely diminished already.
Luckily there is still one company with the guts to market a higher ZDDP oil for passenger cars,in a viscosity that doesn't reduce horsepower: Valvoline. Their VR1 10W-30 racing oil is a quality SH grade oil which simply means the ZDDP hasn't been removed to qualify as a SL or SM grade. Valvoline's MSDS sheet lists it at 1.3% phosphorus/zinc, 1% sulfated ash and 2.5% calcium...which makes for a nice lube cocktail. The new SM grade oils all have about .08% ZDDP to conform to EPA standards while 2% and higher ZDDP is considered the level to use in an older motor. Valvoline states it exceeds SM levels of protection...so this is now my oil of choice, even over a synthetic. Mobil 1 is available in a high ZDDP synthetic but I find it too expensive for my tastes.
Find VR1 in the US at NAPA stores, the Valvoline part# is VV205, around $5.75 a quart or online at Amazon. Sold by the case Napa will likely have to get it shipped in from their warehouse. It also comes in a 20W-50 version but I think that's too thick for a L28 motor.
Oil filters don't increase horsepower or make the engine breathe better...they filter the oil. The particle size considered to cause the most wear is said to be around 15-25 microns in diameter. What you need is a filter which can reliably filter the smallest particle size from your oil supply. Be careful using racing oil filters as many are designed for maximum flow by allowing everything up to 50 microns or so to pass into the engine...which I guess is fine if you tend to rebuild your motor every season.
I remember over a decade ago Consumer Reports named FRAM the best on the market and I used them since 1980 with no problems. However, Fram is starting to include "additive gel" in some filters to "infuse into the oil" which worries me that they're going down the Slick 50 path.
WIX filters appear to be of high quality and filter down to 19 microns. Their advertising is aimed at people who understand engines, instead of the Slick 50 crowd. The filter they list for 1970-83 Z car engines is #51521.
NAPA makes a high-quality filter with part #1521 which filters down to 19 microns and is easy to find. Interestingly, the specs between WIX and NAPA are identical and it appears they may be the same filter. Between the identically spec'd pair I use the NAPA because it's easy to find and buy. The NAPA name may conjure up thoughts of truck parts, but isn't that what you want... a quality filter designed for long service duty?
30 years ago when oils were crappy, using an additive was a pretty good idea. But today's SM grade motor oils don't require them. Enough said.
Nissan modified the L-series oil pump for the 1981-83 Turbo 280ZX to put out more volume than standard Z oil pumps. Labeled “H4” on the side it has a longer rotor/stator inside the body so each rotation puts out more CC of oil. Non-turbo pumps are stamped with H28, H33, etc.
Years ago I was told that the pump for the automatic transmission 280ZX turbo had a higher CC volume per rotation than the manual trans turbo pump. Supposedly this was to provide more oil for the oil cooler which only came on the auto trans model. To back this up Nissan lists two part numbers for the turbo oil pumps: 15010-S8000 for the auto and the more expensive 15010-V0300 for the manual trans model. However, people have taken apart the pumps and both the auto and manual versions appear to be identical with 40mm long stators and the same pressure spring.
So the mystery continues…why did Nissan provide two different turbo pumps if they appear to be the same internally? Regardless, you should upgrade to a turbo oil pump to energize your oil supply and raise the pressure to the rear bearings. But be careful…since turbo/non-turbo pumps are identical externally the auto store might sell you wrong aftermarket one…the only way to know what it is for sure is to open it up and measure the length of the shaft.
I would buy a turbo pump from Nissan, Black Dragon or Motorsport Auto to guarantee you get a real one.
I have used several types over the years. "Open" ones can draw in the hot air from the exhaust manifold which isn't good for power. So here are my recommendations:
STOCK AIR CLEANER MODS
ELEVENTH- the exhaust system
HEADER vs STOCK MANIFOLD
The stock Z exhaust manifold is said to actually flow pretty well for street use. Quiet too. A header uses long exhaust runners to separate the exhaust ports and allow better top-end breathing (scavanging). This occurs because having long exhaust runners keeps each exhaust pulse from interfering with the gases exiting from the others. Because when several exhaust ports open into a common manifold they can cause flow disruption due to the timing overlap between intake and exhaust valves. An interesting benefit of a cam is that gas mileage usually goes up. The standard improvement advertised by header companies on motors is advertised at 5-15hp.
While some people claim a header produces no effect, putting one on a motorcycle requires that you actually rejet (richen) your carburetors because it improves breathing so much. In addition, car legend is that the Corvette 427 L88 motor would pick up 150hp just by adding tuned headers. While I admit that a Z engine in stock form wouldn't benefit much from a header, I feel a L28 with a bigger cam, higher compression and ported head demands one. If you create a free-breathing motor that pulls 7,000rpm, putting a stock 2" exhaust on it doesn't make sense. Every road-race car in the world uses headers...good enough for me.
Headers are made of thin-gauge steel because they have to be bent into shape and welded rather than cast like the stock manifold. The result is that they tend to rust through quickly. The solution is to get one with Jet-Hot or ceramic coating to lower heat and improve durability. If you buy a non-coated header, before you put it on use paint stripper to remove the factory paint. Then prep and spray with a quality manifold heat paint. The paint they are shipped with usually flakes off ...paint it properly before you put it on the first time.
I've used the Motorsport Auto 6-2 header for about 10 years and had no problems with it. In May 2007 I replaced it with a 6-1 version and their premium bolt-on 2 1/2" system. The header has a thick flange with good clean welds inside the header. The exhaust system exceeded my expectations, with high quality 3-bolt flanges both the in front and rear joints...the exhaust hangers were even welded in place. A monkey could put it on. Good job Motorsport!
If you plan on keeping your Z for another 20 years, I would make sure you have an extra stock exhaust manifold in the garage as a replacement. I suspect Z headers will be difficult to find in the coming years as these cars get really old.
The MSA header gasket uses a metallic core which is very similar to the Fel-Pro version. So I have no problem using this new gasket which appears very durable. Again...good job MSA! If you want to use a stock gasket I had no problems using one with my sets of headers. Despite the old wives tale that stock gaskets leak with headers, mine sealed tight as a drum. I suspect that's an old wives-tale from hot rod days.
TIP: use a fine flat file across all the ports on the header flange before installation to take off high spots and make it flush. I believe this is actually where the leaks come from.
The search for the best muffler is as long as the one for the Holy Grail. Everyone has their favorite, but no one is ever satisfied. Here are my experiences and the ones I've tried:
DUAL ANSA TIP: I used dual Ansa tips on my '76 280Z in the 1980s. Good idle tone but raspy under power. Thin wall 2" pipe.
MONZA BIG BORE SINGLE TIP: I used one of these single tips on a straight pipe on my '76. Sounded incredible when opened up but the Virginia State Police gave me a ticket for a noise violation.
SUPERTRAPP 4": I used one of these for about 8 years. Great for tuning the sound using the removable plates. No negatives other than having to keep an allen wrench handy for the screws.
DYNOMAX super turbo-oval 2 1/2": nice refined tone which made the car much quieter, excellent performance. Doesn't fit well under the rear valance though.
MAGNAFLOW 2 1/2" XL turbo: My current muffler seen below. Fits perfectly and looks stock. Around town has a nice sedate rumble but when opened up above 4k it sounds like a machine gun on 110 octane. The welds have an odd brown tint that isn't rust, I would have it Jet-Hot coated if I were to do it again.
People have been arguing about whether to use a 2 1/4 or 2 1/2 " pipe for years. If you are doing competition then a 2 1/2" pipe will add more power on the top end, a 2 1/4" works and fits well for the street. Just don't lose sleep over which is best. NOTE: if you have a catalytic converter, you can only 'legally' change the "cat-back" part of the system. Keep in mind that the Monza and Ansa brand systems are only 2" in diameter (boo). Also, the 240Z came stock with a teeny 2" exhaust pipe stock. Kudos if yours is still intact, but I would replace it with a larger diameter pipe.
HEADERS vs HEAD TYPE
All intake ports from 1969 to 1983 were round, the L28 heads have a notch at the top for the injector. Use a 1970-73 intake/exhaust gasket to cover these if you want to use carbs.
- 1970 through 1976 heads have square exhaust ports (E31, E88, N42)
- 1977-'83 heads use rounder, diamond shaped exhaust ports (N47, P79)
- 1981-'83 turbo heads have square exhaust ports (P90,P90a)
In terms of design I'm been told that '77-83 headers are identical. The difference is that '77-83 versions come with an EGR connection. So if you have a P79/P90 on a carb'd engine, just use a '77-78 header. Just don't obsess and start swapping stock manifolds back and forth. GET A HEADER!
The result is you end up with a stock-looking 240Z with a ZX motor, superior electrical system and ignition, 5-speed, upgraded drivetrain AND a high-ratio rear end. A good old fashioned hot-rod using factory parts! Thank you Nissan for making all the parts interchangeable!
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