For a mild cam, stick around 9.5:1 and you should be able to run around on anything between 87 & 94 octane depending on where you run your ignition timing. This is a very general statement, however. There are several reasons I can run higher compression, the most significant is the 308S camshaft. Right up there is jetting and ignition timing. It's not for the faint of heart and in the long run may be more trouble than it's worth to some people. The important thing is to know what you want out of the engine and then get advice on designing the whole package to get you where you want to be. Cam, compression, intake/exhaust flow, carburetion, final drive ratio, converter stall speed, vehicle weight, etc...all play a role, and messing up just one part of the equation can make for a car that's disappointing to drive in one way or another. Devon
Cool thanks for the info. Have an issue here, I'm looking at a muscle car website and the info on horsepower. My 67 430 produces 360 gross, and the 72 455 produces 250 net. People tell me that you need to subtract 25% from gross to get net. So if I take my 430's 360 and subtract 25% I get 270 net. That is 20 more than the 72 yet is 25 ci smaller. Is this only becasue of the compression ratio, cam and other parts on the 72 causing this lack of horsepower?
Is this only becasue of the compression ratio, cam and other parts on the 72 causing this lack of horsepower? well, there's the whole catalytic converter + single exhaust screwing things up as well. but yeah, all other things being equal a 455 is going to make more power than a 430. they even share the same crank after all.
