p51 cumbustion chamber size

cool40 wrote:Know your valve clearance before you get started cutting.

wayney wrote:boost in cr without getting into the short block.

wayne

wayney wrote: I have been told that there is not much power to be gained in the heads to justify the cost of port work.

wayne

rmcomprandy wrote:

wayney wrote: I have been told that there is not much power to be gained in the heads to justify the cost of port work.

wayne

I guess that would entirely depend upon how much more power you are seeking versus how cheap you are.

10.0 wrote:If you mill a bunch on the heads, they will be less saleable and may have deck problems as well.
Might be opening a can of worms.

Lem Evans wrote:

10.0 wrote:If you mill a bunch on the heads, they will be less saleable and may have deck problems as well.
Might be opening a can of worms.

This statement is spot on.

wayney wrote:

Lem Evans wrote:

10.0 wrote:If you mill a bunch on the heads, they will be less saleable and may have deck problems as well.
Might be opening a can of worms.

This statement is spot on.

this is what i was wondering about. compromising the deck. wondering if anyone had done it .060-.080 in a higher pressure motor. high compression or middle of the road boost/ nitrous.
i am just thinking out loud. if i was going to go through the expense and time of piston replacement i would probably just build a new short block or motor.

wayne

IDT-572 wrote:35 cfm @ 2.25 hp per cfm is right at 80 hp. that's what a good port job with a 2.300 valve is worth. But it's several $ too.

One pint of compression wont get you near that. Maybe 30 HP from 72 to 60 cc chamber.  

Lem Evans wrote:

wayney wrote:

Lem Evans wrote:

10.0 wrote:If you mill a bunch on the heads, they will be less saleable and may have deck problems as well.
Might be opening a can of worms.

This statement is spot on.

this is what i was wondering about. compromising the deck. wondering if anyone had done it .060-.080 in a higher pressure motor. high compression or middle of the road boost/ nitrous.
i am just thinking out loud. if i was going to go through the expense and time of piston replacement i would probably just build a new short block or motor.

wayne

I looked back at some of your post......you have a big dish piston now as I see it?

wayney wrote:

IDT-572 wrote:35 cfm @ 2.25 hp per cfm is right at 80 hp. that's what a good port job with a 2.300 valve is worth. But it's several $ too.

One pint of compression wont get you near that. Maybe 30 HP from 72 to 60 cc chamber.  

don't take this the wrong way your car/ motor runs great and i know you know what you are doing.

if i could get them ported and pick up 50 to 80 hp i would definitely be interested . I know more cfm does not always add a given amount of HP. i have personally changed ported dove heads to ported aluminum cj heads on the same motor in the same car milling the alum heads to gain a point of CR and only picked up .5 mph after tuning. the cj heads flowed 50cfm more than the dove heads (on the same bench) at the dove head peak (.600 lift) and outflowed them across the board. the heads were the only thing changed. Has anyone on here done a A-B ported VS unported P51 head dyno test? The shop that i spoke to about porting the p51  heads is a very competent and respected engine shop . it was a simple question of " on a 521 is there much gain to be had from porting my p51 heads" answer was  " a full competition port job would see 15hp and it is usually not money well spent" . I am not sure what it cost anymore to get the port work done as it has been 12 or so years since i have had a set of heads ported ( cnc c-460 heads ).