compression ratio

[Splitpin]

I'm still trying to work out which heads/cam to buy for my chevy 350. There's too much choice.
Now i'm considering a Trickflow engine kit which has a matched cam. How do I work out the compression ratio for 72cc heads? It needs to be 9.5:1 or higher. They advertise "fair idle,broad midrange power, powerband 2800-6300rpm.
I know roller lifters allow more cam but do you think the advertised duration 292intake/296 exhaust, (or @.050 lift 230 intake/234 exhaust) is ok?
cheers again

Mike

[Paul Gayter]

Hi Mike,

You can do worse than start here,

http://cochise.uia.net/pkelley2/DynamicCR.html

there are two aspects to CR static and dynamic and you need to keep an eye on both especially with the cam you fancy using. My motor has static CR 11.0:1 but DCR 7.5:1. A big issue for Chevy lumps is Squish, it is important to get this correct or your engine could suffer detonation due to pooly mixed charge. There is a lot about it on the web. I use DYNO2003 to give an indication of how the engine will perform. On the last engine I built it seemed to be fairly accurate when checked against performance using a G Meter.

Paul.