I dont know the first thing about what goes into shaving heads, i do know you can get a higher comp ratio by doing it.i have a set of 781's i picked up cheap, im trying to get my comp ratio up, how much can i pick up by doing this? any other things i should think about when doing this? This is on a 402, are these heads gonna work well?
402, 20 over
comp cam 274 280
568 578 lift
domed pistons but dont know off hand how many cc they are
Edelbrock rpm air gap
750 holley.
msd Hei

You will need to know the dome volume of the piston you have & the depth the piston is in the block.
But I can tell you it will take a pretty good sized dome with a 118cc head in a 402.
To get to 9.5 in an uncut block will take about a 36cc dome with a 118cc head.

On your question about "shaving" or milling the heads:
I use .006/cc for flat milling when I first cut the heads but it is actually closer to .007/cc.
I use .006 & then measure again before the final cut as it is much easier to remove material than to add it :D
if you wanted to go from say 9.0 to 10.0 you would need to remove 12 cc's or between .072 & .084 thousands from your heads by milling.

if you wanted to go from say 9.0 to 10.0 you would need to remove 12 cc's or between .072 & .084 thousands from your heads by milling Mike, can that much be taken off the heads without affecting geometry,gaskets/sealing or anything else?

I just went through this. Unless the pistons you have are the real large dome for open chamber heads {dome is over .375" tall}, you probably have the stock 18-19 cc dome {approx .200" tall}. These pistons only yield 8.5/1 CR with open chamber heads. Most of these in an undecked block have a piston/deck ht of .020 to yield a quench of .042 when used with an original steel .022 head gasket. If the modern Felpro type are used {.041 thick), the CR will drop even more. You really need to check your deck ht first. Assuming you can achieve a .040 quench, at a bare minimum, you will need about a 110 cc head to get even close to 9.0/1 CR with stock dome pistons.

If the heads are already off the motor, clean the piston tops and get the numbers off of them and measure the piston/deck clearance with either a dial indicator if you have one or use a straightedge and feeler gauges and that way you can find out what you really have. Anything else is just guessing.

Originally posted by Rapid Robert:
</font><blockquote>quote:</font><hr /> if you wanted to go from say 9.0 to 10.0 you would need to remove 12 cc's or between .072 & .084 thousands from your heads by milling Mike, can that much be taken off the heads without affecting geometry,gaskets/sealing or anything else? </font>[/QUOTE]=
Robert,
If it is done PROPERLY it is not a problem.
The intake side needs to be cut the same amount as the chamber side & in some cases the top of the block but this is rare as long as you use a sealant & not the end gaskets.
There is formula for small blocks on the amount to remove but it is not necessary.

If cut at a 1 to 1 ratio I have never had a problem with alignment & I have whacked a LOT off of some heads :D

I had the block decked, not sure how much, seemed standard for what is done when decking, The pistons ordered were supposed to be bigger than stock dome. I dont have the motor yet, its awaiting final payment so i can get it out. Just trying to figure out where my comp ratio might be. How much does it usually cost to have heads shaved??

Anthony,

You are going to have to get the specifics together in order to figure this out. Without some identifiable part numbers and measurements, there's no way to know what you have.