[georgia_stang]

GT-40P heads came with my 302 and i was wondering if they can be milled to increase the compression slightly...also, if they can be milled, does anyone know by how much??

[e3sean]

not sure i have the same question though they already have a small combustion chamber. with my flattop pistons on my 347 stroker they will make just about 10:1 and i want to raise it to 11:1

[ryans88gt]

11:1 is kinda high for pump gas, I'd go 10.5:1 tops.

I think Jbig had his milled...JBIG??? Where are you?

[Racinjason81]

if you mill heads too much the intake may need to be milled.GT40p heads dont flow that well so why dont you invest in some better heads?

[e3sean]

the invest word is expensive. lol i plan to get some trick flow or afr heads but i have to pay my cc down from the 2500 hit for my stroker kit and the machene work that had to be done. ok so if they ar sitting at 10:1 and the combustion chamber is 59-61 cc how much would i need to get them milled to get the 10.5:1

[JBIGBOOTSY]

.030 will give you aprox. a .5:1 compression bump

[JBIGBOOTSY]

Gt40p heads are 58cc to start with, so after .030 your sitting an angles fart shy of 10:1

[e3sean]

all the research i have done says that gt40p heads are from 59-61 cc depending on the year of them. so .030 will give me .5 is there a formula or guesstimate of how much power that will add?? and can i run 91 octane on 10.5:1 i havent founf 92 yet

[baine21225]

93 octane

[ryans88gt]

Originally Posted by e3sean all the research i have done says that gt40p heads are from 59-61 cc depending on the year of them. so .030 will give me .5 is there a formula or guesstimate of how much power that will add?? and can i run 91 octane on 10.5:1 i havent founf 92 yet

Should give you 5 hp?

[1slo5.0]

With a flat top piston with a typical 4cc valve relief, a 4.100 bore .040 compressed head gasket, 4.030 bore x 3.400 stroke, zero decked and a 58cc chamber you will be at 10.78:1. I wouldn't mill them at all if you plan to run pump gas.

[e3sean]

Ford Head Flow Data and Specs this here says 59 cc so i think i will avoid walking on thin ice and not mill them..

[tmoss]

they vary either side of that spec - gotta burrette em to be sure. Mine were set up (not by me) at 59.5cc for a 59cc limit F/S class.

[georgia_stang]

hmmmm, now i'm not sure if i want to mill those heads....

the engine came out of a 2001 explorer, and only had 80,000 miles on it, but the heads look practically brand new....i already have the B303 cam for it, along with the unilite distributor, promaster coil, edelbrock performer intake, and a holley 650 double pumper...if that's too much carb for it, i can trade it to a friend who needs it for his 350 chevy engine...

i just need the T5 tranny now, along with the king cobra clutch, and all that gets dropped into a 1988 jet black 2700 pound mazda RX7 convertible...i am also having flowmaster mufflers installed along with a 4 point rollcage, and i was also considering a small bottle of NOS in the trunk...that car should be SCARY fast when we finish building it.