Compression Ratio's

[Dan]

I just down loaded the L6 engine calculator and now my head is abuzz with questions. Playing around with this usefull program i noticed how easy it is to raise the compression ratios of my L24. For instance swapping my E88 head for a E31, or replacing the crank with a later model unit. My question is how much compression can you run and still use regular pump gas. Also does more compression necessarily mean more horse power. My qustions are really just academic since this is all part of the learning process. Fear not i'm not going to go out and build an engine that will blow me the car and my neigherhood up:D Building engines is beyond my humble skills right now but i do love to learn.

[2ManyZs]

Yes, more compression will give you more hp. How much will depend on the displacement increase along with the compression increase.

IMO a compression ratio of 10.5:1 would be about the max on todays pump gas, even at that you would need to use the highest octane available to ensure that you won't get any detonation. Most high performance cars today run about 10:1 to 10.5:1 but as you know the ignition systems in those cars make a Z look pretty archaic. You would probably need to upgrade your ignition system as well. At the very least you would need to upgrade to a hotter coil, with some of the better plug wires.

The E-31 head is one of the better heads that came on an L series engine, but they will not breathe as well as some of the later heads since they and the E-88 have smaller valves. Luckily you can swap in the larger 280 valves easily, most any machine shop should be able to do it for a minimal cost.