Quote:
Originally Posted by Bad70sbchevy
I agree, a big cam is NOT good for engines seeing low rpms, but a big cam will make more power, it just happens at a higher rpm due to overlap helping cylinder scavenging thus increasing volumetric efficiency. Also on engines, shouldnt you always shoot for the highest compression ratio possible (without detonation) since it results in higher efficiency thus leading to more power? Any time you raise compression you should always see a power gain (in theory), even if its a little bit. I wouldnt call it a bad combo, just probably not for a PURE street engine.
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A big cam isn't going to make more power unless the heads can flow to the level of that lift. As an example, a big cam with 882 heads even if they're ported to a crazy extent isn't going to make power at high RPM...it just can't flow enough to use what the cam offers. And overall - a big cam making power at a crazy RPM level doesn't really do any good unless the car is regularly at that RPM level.
Compression ratio does improve volumetric and combustion efficiency...but again, only if the engine can make use of it. The more flow the engine can consume, then the more important CR becomes. Premium pump gas limits CR to around 10.2 with full ignition advance and an .040 quench....that's just as far as we can go on the toilet water we have for gas today. Going higher than that means giving up power - backing off on ignition advance or the previously mentioned DCR. For an engine running on pump gas, that 10.2 or so is the Golden Rule for a GEN I. We can push that a fair bit on a GEN II or LS due to the dramatically better combustion chamber shape, and even a bit with top-notch heads on a GEN I...but the gains are minimal unless it's a very hot engine. Vizard has an interesting chart that shows the benefits based on HP/CID - I'll see if I can scan and post it.
I would call the OP's engine a really bad combo. It can be made to work, but it's never going to work particularly well. The only thing we can do is figure out the crutches it's going to take to make it work without coming apart, and there have been a lot of good suggestions around that...but if budget is not an object, swapping the heads to get the CR into a reasonable place is the best choice.
Again, not trying to be
but this is the way it is
