i was going to rebuild my motor, but after thinking more about it, im thinking i want to just do a head and cam package...the motor has 134k on it, but doesn burn any oil, runs amazing for that many miles...so at most im going to freshen up the bottom end...but i want to run about 11:1 CR or close to it...can you shave enough off stock heads to do that?...or would i have to go with heads with smaller combustion chamber?...the plan is cc306 cam and ported lt1 heads...but i want more compression too...any input will be appreciated

 

Well, milling the heads will get you a little bit, but if you really want to change it put in different pistons.

 

Sorry to say but the best way to raise compression is to go with a Dome Style Piston. You can also try running Impala Head gaskets.

 

i know pistons are the best way, but i dont want to buy new pistons...between decking and the thinner head gasket, is it possible to reach 11:1 compression on stock pistons?

 

This should not be a problem. Run the compression calculator and it should tell you the story. Try calculating a 52 cc chamber, and .029 gaskets.

 

whats a compression calculator?

 

https://www.camaroz28.com/calcs/index.shtml

look for the compression ratio calculator.

 

I got to 11.8:1 with an Impala head gasket and heads that were milled 0.030". You need more than just the static compression ratio. You need to look at the dynamic compression ratio. With a bigger cam, it changes the times at which the valves open and close, so the cylinder pressures with the engine running are very different. For example, I run a 230/236 cam. With the 11.8:1 compression the dynamic compression ratio is not too much higher than stock. With a stock cam, the engine would probably not run very well, since it would be likely to detonate.

BRAD

 

The best way to raise compression to the range you are looking for is to deck the block so the piston is sitting .001" to .005" down in the hole. With the Felpro gasket (.039" compressed) your quench height will be .040" to .045". This is about as close as you would want to run to prevent piston to head collisions when the rods elongate/stretch when they warm up and are spun fast and the piston rocks in the bore. Minimizing the quench height does wonders for reducing detonation due to extra turbulence in the combustion chamber caused by the tight squeeze in the quench area. Many people try to reduce detonation by adding a head gasket and lowering the compression ratio only to find that the detonation problem has gotten worse because of the reduced turbulence in the combustion chamber.

It's not the easiest way but your subject was the BEST way.