I was trying to figure out my compression ratio for my engine.
its a 350 bored .040 over with a set of after market piston. The Pistons have .020 whacked off the tops. The engine was not decked or anything just bored. I also, have 416 305 heads to go on top which are fully ported with 1.94 intake valves. I want cr of atleast 10.5-10.7. I know with these piston the cr is going to be like 9.8 or something. Should I get the heads milled to 54 cc?

 

What head gasket?

 

A regular head gasket that you get with a rebuild kit. not steel shim.

 

You need the Specific Bore opening of the gasket and the compressed thickness of the gasket that you have selected, otherwise, no one can help you. Also, do your piston have valve reliefs or dished tops? How far down in the hole are the piston crowns? Stock GM pistons usually run .020-.030 down. Many after-market pistons are sometimes de-stroked .025. If you have cut an additional .020 off the top, you can see the problem. You are not giving enough information to calculate an accurate answer.

 

the pistons have the valve reliefs and the crowns are about 3/8" down from the bore. I wanted to get the block decked because of this but didn't have time. Like you said the piston is destroked .025. The head gasket has a really large opening. I can see like a good 1/4" of the block all the way around. Also, I do not know the thickness of the gasket but it was a regular cardboard type gasket with the metal rings around the bore.

 

 

Yeah I know, but thats what I measured with a measuring tape.

 

You'll have 6:1 or less.

 

This might help it allows you to calculate dynamic and stack comp provided you know some of the engines specs. This is the link for a ton of calculations.

http://www.wallaceracing.com/Calculators.htm

 

sorry about the 3/8. I turns out that the crowns are like .045 from the top of the block. The crank wasns't turned all the way. I did a compression calculator that THETANK had in the url and the compression is going to be about 10.1. Thanks everyone