Datsun-Nissan cylinder head timeline

DatsunZGarage.com

The E30 is the head from Fairlady 2.0 6-cylinder motor. The Fairlady was the Japanese version of the 240Z released in 1970 in America.
The E31 is an uncommon, desirable head that came on many 1970 240's. It's chambers were high-quench designs, however the valves were smaller than the 260 and 280 heads. Probably about 10,000 were made. After 37 years, most of them are long gone having been over-collected and used up in racing. 42cc chambers I believe.
The E88 came on the 1971-73 240s and '74 260s, in 2 versions, small valve on the 240 and larger valve on the 260. It's chambers are the same cc size as later N42 and 47 heads. Despite what some older books say, I can't see why the E88 would have any performance advantage over any other head.
The larger valve N42 came on the 1975-76 280Z. 48 state U.S. 280Zs didn't use a catalytic converter until 1977, so the head came with softer brass valve seats for use with leaded gas. Many people like these for performance because of it's square exhaust ports. And as a easy mod, putting it on a flattop L28 motor puts compression in the mid 10's.

The N47 came on the '77-80 280Z(X). It has diamond-shaped exhaust ports with emission liners, which some feel reduce flow. Starting in 1977 Nissan heads came with steel seats for use with unleaded gas. Like the N42, putting it on a flattop L28 motor puts compression in the mid 10's.

The P79 came on 81-83 flattop piston L28 (F54) blocks. It has a 53cc chamber and must be used with flattop pistons or compression drops to 7.8:1 (with dished pistons). The exhaust ports/liners are identical to the N47, and used an internally oiled cam. My P79 page .

The P90 is the turbo head from the '81-82 ZX. It has the same combustion chambers as the P79, but has square exhaust ports like the N42. The P90 and P90a are said to be the best flowing heads due to their turbo origins. They both use an internally oiled cam. My P90 page.

The P90a is an interesting turbo head which I believe came out in 1983 only. It has hydraulic valve lifters instead of standard rocker arms, which make the engine almost silent. It has identical chambers and ports to the P90 and uses an internally oiled cam. I think with a low lift, higher duration cam this head would be a hot setup. But the manuals say nothing about servicing it and replacement lifters do not exist anymore.

Y70, E80 I've heard these heads were used on Australia/New Zealand Z's. The AU E88 was used on L28 motors. Interestingly, while the 260 was only made in 1974 in the states it was made until 1978 or so over there. I believe they had leaded 96 octane gas until the early '00s, so these may have been higher compression heads, or ones designed for leaded gas. A friend of mine has an E88 with injector ports on his L24, he suspects it received an Austratlian head at some point.

EVER WONDER WHAT COMPRESSION YOU GET BY BOLTING DIFFERENT HEADS ON DIFFERENT MOTORS?

While these specs are reasonably accurate, remember that just having a higher compression ratio doesn't guarantee better performance. Conventional engine wisdom is not to match dished pistons with chambers designed for flat pistons. The clearances and quench shape will allow the flame kernel to spread away from the spark, instead of being quenched into it. As a result it's easier for the motor to get 'pingy'. Aluminium heads can run higher compression before pinging than iron The highest compression you can use on the street with 93 octane gas is about 10-10.25:1. A quality ignition will help you run higher compression without pinging, as will richening the mixture.

But rather than partake in the "which is best" game, keep in mind that compression aside, using the stock large valves, and ported to hot specs, they all work pretty much the same. Also keep in mind, these heads are approaching 35 years of age and may have been shaved/rebuilt before you got it.

WHY DO THE SHOP MANUALS SHOW CONFLICTING HORSEPOWER RATINGS?

Two words: NET and GROSS

Back in the 1960's when the American car companies wanted to advertise giant horsepower ratings, they hit on a devious method. Instead of testing an engine in a car, they would fine tune it and test it in a climate-controlled room on an engine stand. Under these perfect conditions, with no belts, AC, or powertrain to worry about, these engines would produce much higher horsepower than an engine on the street could hope to reach.

Finally the government stepped in the early 1970's, and required that the companies test engines in the car, with AC and other accessories on and measure it at the rear wheels. GROSS HP was the old method, and NET HP is the (more realistic) new one. Subtracting about 20% from GROSS gives you NET. Adding 25% to NET gives you GROSS.

During this period (1971-74), between the insurance industry raising rates on high horsepower vehicles and the ecology movement insisting on better emissions, car companies were forced to lower both. So they dropped engine compression, installed emission camshafts, and leaned out the carbs. Naturally because of the new air pumps and hoses, people blamed them for the loss of power. I actually remember people removing hoses and blocking off solonoids on their V-8s thinking they would pick up lost horsepower. Good try, but it was mainly the lower compression and poor carburation that slowed most cars down in the '70s. Even the Z was affected with crappy carbs and air pumps in 1974, while the move to fuel injection on the 280Z has been said to have been more for emissions than performance.

Datsun somehow got away with using the old GROSS horsepower rating through 1978, probably since they were an import company. All their cars from 1979 onwards use the NET method for horsepower. So even though '75-77 engines say "170hp" on the little plate in the engine compartment. You notice a little "SAE" (Society of American Engineers) printed there as well...this is a subtle way of saying GROSS.