[4spdss]

My son and i just built a 350 for his 88 Monte SS and was wondering how to determine the compression ratio on the motor (We have been looking at 5psi superchargers). The motor is a 1988 350/060 over, flat top pistons and stock 062 vortec heads.

[cobalt327]

Originally Posted by 4spdss

My son and i just built a 350 for his 88 Monte SS and was wondering how to determine the compression ratio on the motor (We have been looking at 5psi superchargers). The motor is a 1988 350/060 over, flat top pistons and stock 062 vortec heads.

• Bore is 4.06".
• The stroke is 3.48".
• The gasket bore diameter is around 4.09" and the thickness you should know.
• The combustion chamber volume is around 64cc.
• The piston dish volume is about -5cc for valve reliefs
• I'm guessing you didn't measure the "Piston Deck Clearance" (how far down the hole the piston was at TDC), so if the block is uncut, that's going to be about 0.025".

Use the calculator HERE, plug the numbers in as best as you know them and see what you get.

[4spdss]

Dude....i appreciate the reply but i'll be honest back in the days of Math class i had a Big Block chevelle and spent most of my time in the pool hall instead of math class. Maybe my son can figure that one out,he's a collage kid. LOL/Thanks

[cobalt327]

Originally Posted by 4spdss

Dude....i appreciate the reply but i'll be honest back in the days of Math class i had a Big Block chevelle and spent most of my time in the pool hall instead of math class. Maybe my son can figure that one out,he's a collage kid. LOL/Thanks

The only number I didn't give you is the head gasket thickness (common size is 0.041" if it's a rebuilder type composition HG). The calculator does all the work, all you have to know how to do is type in the numbers.

[whyholdback]

With FelPro 1094 steel shims, your quench will be correct, but you'll be around 10.5:1.
With the ZZ4 head gaskets you could get around 9.7:1, but that's still too much for 5 psi, especially with such poor quench.