MODIFIED 1983 280ZX F54/L28 with SU CARBS
After almost 30 years of driving, modifying and racing Zcars I decided I wanted to now the answer to the big question: how much power do you really get out of a SU-carbed L28. I'm not talking about a stroker, turbo, or nitrous engine but an Old School L28 motor with a cam and header, running SUs, electronic ignition and maybe a little compression boost thrown in.
Keep in mind that Datsun 240Zs were designed for road racing, not dragracing, so don't let the moderate dyno numbers fool you. A 2300 lb 240Z is very similar to a Lotus from the same period...the stock engines weren't very torquey and horsepower not high, but the cars could accelerate fiercely and were very responsive on the track, especially when modified properly. In the early 1970s at Lime Rock racetrack in Connecticut they were known to routinely beat 427 Cobras and Porsches that ran with much higher horsepower.
So after several years of mods and engine work my inline-6 engine is completely streetable. It idles at 900rpm, pulls hard throughout the rev range to 7000rpm, and will reliably pull a 1/4 mile in the high 13s/low 14's. It is very loud at full throttle and sounds like a vintage racer...which it is. The trick is finding the combination of parts that maximize power over a broad range while avoiding power spikes and dips. While some people claim to see 220+ horsepower at the rear wheels on their street L28s, I'd like to see those dyno sheets. Detailed experiences online show that modified SU carbureted L28s on 93 octane seem to max out around 160-170 at the rear wheels (210 hp flywheel). Stroker motors can break this ceiling as can expensive fuel-injection and three 2-barrel Mikuni/Weber carbs, but I have none of those. So my results are pretty good for a 40 year old car with 27 year old engine and stock carbs.
DYNO FACTOID: There are two major brands of engine dynos on the market. Mustang and Dynojet. (Note: Mustang Dynamometer is not affiliated with Ford). Mustang says their dyno approximates real world "street" conditions, Dynojet is the industry standard and is more mainstream. The problem is that because of the way they measure power each type will give you different results. What makes it trickier is that there's no real way to compare the data between the Mustang and Dynojet.
The proper method is to run your car on one dyno, make modifications and then run it again on the same dyno. Then you can accurately gauge what effect your mods had. In other words a dyno should be used as a progressive diagnostic tool rather than an absolute judge of your power.
But because I ran my car on a Dynojet in 2007 and then a Mustang in 2009 I caused confusion for myself as I can't really tell if my power went up, down or stayed the same. Why did I use two different dynos when the results are not comparable? The reason was that the shop near me with a Dynojet won't answer the phone or their email and I was anxious to see what my new mods did. So I decided that questionable results were better than nothing. The air/fuel measurements are accurate between the dynos, which is what I really needed to know to gauge my new SU needles.
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