i have a 12 valve carbureted prelude (1985, 1.8 dual carb 3bbl), a 16 valve crx dx (1990, 1.5 dpfi), and a 12 valve crx si (1986, 1.5 mpfi). i am rebuilding the dx and doing an engine swap so i bought the prelude (it was really cheap and in great shape). the crx si is a parts car, but only for the race car that i have (another of the same crx's). my question is, can i change the compression in the prelude by changing the cam with the 12 valve or 16 valve cam from one of the crx's? will that make a good change? the other part is, will putting the prelude cam in a crx, if it fits, be a good change too? OR does anyone know how to change the compression on a stock head without buying anything? is there a way to manually adjust the compression to get more of it?

also, what does changing the compression do to an engine? does it make a noticable difference if the car has more compression, or less compression?

 

anyone? just because it is carbureted doesn't mean you don't know . . . . . . has anyone ever tried something like this before?

 

I dunno about the specifics of the question you're asking, except to say that fuel injection is almost always better than carburators. When it's all said and done, you will always get more HP from a fuel injected motor because a carburated intake manifold tops out at around 85% volumetric efficiency vs. nearly 100% for fuel injection (on a well designed TB/manifold setup). This is because a significant amount of vacuum is required to allow the carbs to work properly, while fuel injection can function perfectly under ideal WOT conditions which would be close to zero vacuum.

How's that for hazy, useless, and incomplete information?

 

thank you for that info - however, i have found that i am not looking to increase the compression, but advance the timing to get a higher top end. thanks anyway