I opened up my p72 combustion chambers to 84mm and also deshrouded. I cc'd the chambers to 44cc's each. Stock is around 41.60cc each according to the C-Speed compression calculator. I want to get the head milled to return the volume close to or right back at 41.60 or so. How do i figure out the amount of milling to achieve this? Thanks techies.

 

well u get a 9.58:1 CR with stock internals and stock hg and no milling with your 44cc volume..

Im using stock just for an example here..

so..stock cr is 10:1

so start by taking off hg thickness on the calculator...

You want to get that cr back up to around stock:

so stock is .029, take .005" off, gets you to 9.69:1

" " take off .010" nets you 9.8:1

" " take off .015" net you 9.9:1

" " take off .020 net you 10:1

there ya go...this gets you back to near stock volume..

you can do this buy using a 2layer hg. of .4mm which is .015748 - .029000 stock thickness = .013252 then mill .006"..

Cheers

 

but since you are trying to reduce the physical volume, not buy using a smaller hg , you would need to mill all .020.. which i wouldnt recommend if you are using high lift cams and big dome pistons

 

Skunk stage 2, and Wiseco 11.8:1's. Before I touched the chambers I ran a 1 layer w/ the cams and pistons. And it was 2 layer before I pulled the head again. I do want to be able to run a 3 layer stock gasket. Hey thanks for your time JH4DC4-2GSR.

 

Sweet good deal man! hope that helped you out a little and gave u a general idea..

So hows that thing run? any slips etc? I would like a list of mods etc? To get more entusiasm into my gsr build

 

oh it runs damn amazing especially with the 4.78-b16 gears. i haven't drag it at the track. i don't have a good drag wheel/slick combo for type r five lug/brakes. all we have is 1/8th mile local...my guess is deep 8's in the 1/8th, but i would like to spray it. i'll be taking pics of the portwork and heavily modified gsr intake manifold for documentation since i'll probably sell this hatch soon.