If I have a set of 9:1 CR piston that are rated at 9:1 with 119 cc chambers, and I have a set of milled 049's with 110cc chambers, whats the new CR?
Thanks a lot,
Chris

Depends on your deck height and head gasket thickness, (and bore I think). But it should be somewhere around half a point.

Originally posted by Twilightoptics:
Depends on your deck height and head gasket thickness, (and bore I think). But it should be somewhere around half a point. Thats what I was looking for. Just a general answer. Thats perfect. Thanks,
Chris

Try the ROSS Racing Pistons site's compression ratio calculator.

And put in .025" for down in the hole, your two chamber cc's and headgasket thickness.

.020" for Mr. Gasket steel shims up to about .038"/.040" for stock type composites...

pdq67

seems like I read its 1 comp. point for every 6cc reduction or increase,but all that other stuff comes into play too.

I did just a basic 350 in Pat's calc. I don't know any big block specs, but it was worth half a point changing the CC. I tried it with different bores/strokes too. Same result.