we all know head chamber, bore, and head gasket effect compression, but does the stroke? say going from a 355 to a 383?

 

Yes of course.

Compression ratio is the ratio of the cyl volume when the piston is all the way down, to the olume when it's all the way up. Obviously the volume when it's all the way up is the same, regardless of CID (assuming the same deck height); but the volume when the piston is all the way down can be considerably different, since that's equal to the CID plus the "all the way up" volume.

 

The length of the rods, stroke, and deck height you have will help you determine the appropriate piston compression height you need. Most piston manufactures will show you compression height for each of their pistons.

 

Apparently thirdgen refuses to let me to link it. I will type it out.

To calculate the compression height, use the following formula:

Block Height minus 1/2 the crank stroke, minus the rod length, minus the deck clearance (amount piston is "in the hole").



For example, a 350 Chevy engine with a stock 3.480 stroke, stock length 5.700 rod, standard .017 deck clearance and standard 9.025 block height would be:

3.480 stroke divided by 2 = 1.740

9.025 - 1.740 - 5.700 - .017 = a compression height of 1.568.

You should be able to calculate your compression very accurately if you measure everything accordingly. For instance measure your piston to deck clearance and cc your head chambers. They have calculators that will let you input gasket volume as well to get very relaible compression ratios.

http://kb-silvolite.com/calc.php?action=comp

 

second question, how much? say 355 with 10.5:1 going to a 383, it did have desk top dyno, but seemed to have lost it


edit, your post showed up later, didn't see that