Milling P51 Heads
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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?
quikmule84- Posts : 5
Join date : 2013-03-06
Re: Milling P51 Heads
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.
I've ha CJ heads decked to 62cc and slotted intake holes and made intakes work with out milling them.
dfree383- BBF CONTRIBUTOR
- Posts : 14851
Join date : 2009-07-09
Location : Home Wif Da Wife.....
Re: Milling P51 Heads
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.
supervel45- Posts : 4499
Join date : 2013-09-04
Re: Milling P51 Heads
What ever you mill the deck just cut the intake face half that and the intake will bolt right up.
IDT-572- BBF CONTRIBUTOR
- Posts : 4628
Join date : 2008-12-02
Age : 63
Location : Shelbyville Tn.
Re: Milling P51 Heads
Ok. Thanks for all the advice. Also, generally speaking, how far can I mill the heads before having to change pushrod lengths.
quikmule84- Posts : 5
Join date : 2013-03-06
Re: Milling P51 Heads
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.
IDT-572- BBF CONTRIBUTOR
- Posts : 4628
Join date : 2008-12-02
Age : 63
Location : Shelbyville Tn.
Re: Milling P51 Heads
is there a specific amount to mill per CC of chamber reduction? ex. .005 per CC?
wayney- Posts : 187
Join date : 2013-02-19
Age : 56
Re: Milling P51 Heads
http://www.wallaceracing.com/millcalc.php You could run the numbers through here.
supervel45- Posts : 4499
Join date : 2013-09-04
Re: Milling P51 Heads
If I remember right it's about .0055 to .006 per 1 cc
IDT-572- BBF CONTRIBUTOR
- Posts : 4628
Join date : 2008-12-02
Age : 63
Location : Shelbyville Tn.
Re: Milling P51 Heads
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.
supervel45- Posts : 4499
Join date : 2013-09-04
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