I have 452s on a low comp 440. I don't have the money to do a piston swap so I was thinking about having the heads milled. How many thousandths would it take to raise compression half a point?

 

i found one CR calculator. there are others. but this one is easy to use. ask around as to how much octane that will work with how much CR. https://www.rbracing-rsr.com/compstaticcalc.html ,,,,dont for get the Marvel Mystery Oil. 4 oz to 10 gal gas. my engine starts faster with it. been using it for 30 years.

 

Cutting .0042" removes 1cc. Head is about 90ccs. Some have removed up to .080".

So, 80thou = 19ccs. 90 minus 19 = 71.

All of this can easily be searched out but buying a modify your Big Block book would be a good purchase.

Removing .010" from head requires .0123" from intake surface.

Did a quick calc. with thin gasket and this would raise compression 1 - 1.5 points.

Forgot to mention, this type of modification with a bigger than stock cam and pistons with no valve notches can get tight and careful clay assembly would be recommended.

 

I would wait till you could do the whole motor...
Sometimes other issues come up when you start cutting on these heads that much..