I need help in calculating a compression ratio. I have searched and found formulas but I can't get it to work right. Please help if you could.

These are the details:

Stock 5.7 Block
Forged Flat Top pistons
4.8 heads (209cc intake/63cc chamber)
Valves 1.55/2.02

 

What are your cam spec's?

 

Cam card reads:
Gross Valve Lift .608 / .608
Duration at .006 289 / 289
Lobe Lift .3580 / .3580
Lobe Separation 116

let me know if you need more info...

 

Are your pistons in or out of the hole? How much? What bore size are the pistons? What head gasket are you going to run?

 

I get 10.48 roughly. This is assuming you don't have valve reliefs in the piston... if you do it'll be closer to 10.

3.9 bore
.05 gasket
.01 deck

 

Pistons are level with the top of the block. Pistons are factory bore and I do not believe they have valve reliefs. Not sure which head gaskets yet.

I am trying to get a rough estimate for CR ratio. I was told that my cam was great for a turbo and I figured I already had forged pistons and rods.

Assuming the CR Ratio is around 10.5 : 1, is this too high to run a turbo?

 

Its not to high considering people run turbos/sc’s on stock vettes, which is right around the same 10.5:1, but is it ideal or going to give the best gains, probably not…