Milling GT40Ps for smaller combustion chambers...how much?

[85_SS_302_Coupe]

I'm curious what the typical amount of milling people have done on a set of GT40Ps (or any head really) when trying to increase the combustion chambers. I suppose that would depend on the head and the size of the chambers, but lets say we're doing the P's. How much would you have milled off and how high can you get your combustion ratio by doing so? Lets say i wanted a 10:1 ratio with stock pistons...can that be done and if so how much would you have them milled?

[BIZLE]

.030 on my p heads

[transman]

.030 on my p heads

i 2nd that:bigthumb

[Gearhead]

I'm curious what the typical amount of milling people have done on a set of GT40Ps (or any head really) when trying to increase the combustion chambers. I suppose that would depend on the head and the size of the chambers, but lets say we're doing the P's. How much would you have milled off and how high can you get your combustion ratio by doing so? Lets say i wanted a 10:1 ratio with stock pistons...can that be done and if so how much would you have them milled?

GT40P's have 59 cc chambers, so I probably wouldn't mill off more than .030 like Bizle and Transman said. That should put you right about 10:1 with the factory 5.0 HO pistons.....

[85_SS_302_Coupe]

Awesome guys thank you. What's the going price to have this done? Also can you give me an idea of the max lift cam you've been able to run without notching the pistons or anything like that?

[aperacer]

i am running a x-303 cam with 1.6 rockers. .042 thick head gasket. heads milled .030 and the block zero decked.

[BIZLE]

hucks will charge you $100 to mill them
i have ran a tfs1 and a f cam with no problems

[85_SS_302_Coupe]

Cool....do you know if Hucks does the cc test or whatever to find your final chamber volumn? I'm asking all this for a buddy but i'm also interested in getting my Windsor heads milled.

[Timido]

http://besracing.com/services.html
BES prices They say $40 each head up to .030 CCing one cylinder shouldnt cost much either. I like the gt40 combo. I miss driving my old car on the street it was a blast wit the little P headed stock cam.

[85_SS_302_Coupe]

Ok one last question on this one. What is the formula for figuring up your compression ratio? If i know the chamber size of my heads ('69 351W), how do i figure out what a .030 milling will give me as far as the ending chamber size and compression ratio?

[Timido]

You need to know alot of details but this will get you close. http://rosspistons.com/calculator.php

[leroy93lx]

I have gt40p's i got from TriState Cylinder heads with 1.94 1.54 valves, can i take that same .030 off safely with an Anderson N-21 cam and stock bottom end?

[Timido]

The only way to saftly make changes with yours or any combo is to check piston to valve clearance either with clay and measure it or with a dial indiactor a degree wheel and a spring checker spring.

[leroy93lx]

Thats what i figured. Better safe than sorry. I was hoping to hear exactly what i wanted so i could be lazy and just bolt them on and go! HaHa!

[leroy93lx]

What about the pushrods? If you take .030 off can you or do you run stock pushrods?

[ClevelandMstang]

What about the pushrods? If you take .030 off can you or do you run stock pushrods?

Pushrods will be fine, after around .50 you need to run shims on the rockers.

Always check PTV clearance, not always about the lift, duration plays a bigger role in it.

I would not mill more then .40 at most, these heads have a thin deck and you will create head gasket issues.

[leroy93lx]

Thanks for the info. I appreciate it!