GT-40P valves

[BeauJ]

What's the biggest valve size, intake and exhaust, you can put into to the GT 40P heads ?

 

[plrs x45]

You should put 1.94/1.60 in there. Putting valves that are too big does nothing. On mustangs, mild mods (under 350hp) sometimes required a porting and not making the valves any bigger (1.84/1.54 I think). A mild port may be of bigger advantage to you. Good luck!

 

[james t]

GT-40= 1.85/1.54

GT-40p= 1.85/1.46

you can go considerably bigger on the exhaust, but not much bigger on the intake. 1.94's are possible on the intake, but need to be done by someone who REALLY knows what they are doing.

unless you are planning on running over 380hp, there is no need to change valve sizes. you can get what you want with good porting. what is it you want to do with the motor?

 

[BeauJ]

I'm planning on getting it in the 400-425 range, and right now im saving up for the custom headers. Why would it be so difficult to get someone to put 1.94's on the intake side and really be careful ?

 

[james t]

because you have to grind on the spark plug boss. no big deal, as whomever would be doing the work on cutting the heads for bigger valves will/should know what to do. also understand, 1.94's plenty big enough for 400hp.

 

[plrs x45]

I went 10.56 with my mustang on 1.84/1.54. Find a good porter and you will be set. Good luck!

 

[fastford]

for the price of the machine work you can throw in a little more and have some better heads all together you are building custom headers anyways spend some money and get the aftermarkets heads of your choice afr,trickflow,world pruducts ect ect