Milling P51 Heads

Have a 501 BBF with @ 12:5 compression, race only. Would like to increase compression while motor is out. How much do the heads (P51's) need to be cut to pick up 1 point of compression? Would like to end up between 13.5 to 14.5 comp. Pistons in the hole .005. How far can I go before getting into intake alignment issues?

At .030 it's going start affecting bolt holes on the intake.

I've ha CJ heads decked to 62cc and slotted intake holes and made intakes work with out milling them.

http://wallaceracing.com/cr_test2.php If he has 72 cc's now and goes to 62 cc's he should be in the low 14/1 range with flattops and 0ne 3cc valve relief.

What ever you mill the deck just cut the intake face half that and the intake will bolt right up.

Ok. Thanks for all the advice. Also, generally speaking, how far can I mill the heads before having to change pushrod lengths.

quikmule84 wrote:Ok. Thanks for all the advice. Also, generally speaking, how far can I mill the heads before having to change pushrod lengths.

.050 makes a difference in your rocker geometry. but you need to see how it looks now before you start.

is there a specific amount to mill per CC of chamber reduction? ex. .005 per CC?

http://www.wallaceracing.com/millcalc.php You could run the numbers through here.

If I remember right it's about .0055 to .006 per 1 cc

For what it's worth that calculator comes up with .2 points of compression increase with a 4.15 stroke crank and .005 removed, with a 12.5C/R as a start. It mentions Pontiac so be aware of that.