I am building a 350 engine for my firebird and i am about to call Comp Cams for a cam recommendation. I was wondering if anyone could help me figure out the compression ratio because Comp wants to know it before giving me a recommendation. The engine is an 89 350 truck engine, i have some Vortec heads coming(stock, but i will modify them to get more lift, but i dont think that affects comp ratio), a Edelbrock Performer RPM intake, and the block is stock bore with flat top pistons. I just dont know how to figure the comp ratio.
Thanks, Dave

 

Go here for an online calculator that will get you close.

http://www.csgnetwork.com/compcalc.html

For piston deck clearance, I've measured between 0.020" and 0.025" for
most SBC's.

You will need to know the cylinder head chamber volume in cc's, along with
the compressed gasket figures.

 

online cr calc http://www.wheelspin.net/calc/calc2.html

bore 4.00
stroke3.48
cylinder head chamber volume 64cc
Head gasket diameter 4.166" x .040" Felpro composite
"" " " 4.10" x .015" felpro shim gasket #1094
Shim gasket gives proper net piston deck quench clearance and .5 more compression ratio.

Piston dish or dome +w/valve relief volume (flat top 4 valve relief)-6cc
" " " " "(factory dished w/reliefs)-12cc -15cc
Typical

Piston deck clearance @ TDC .025" nominal.

Enter the numbers in the calc to see how your real compression ratio can vary according to the gasket used and the piston type.

http://www.wheelspin.net/calc/calc2.html