coony278

What is the difference between a GT-40 head and a GT-40p head. I have a set of both and cant physically see a difference.

Well I guess the one set is GT-40 heads , they only have GTembossed on them but the GT-40p heads have GT-40 embossed on them.

Which one is suppost to be better?

thanks

Chad

dimebag

i think p's are "better" something like a 9.5-1 comp... and better exhaust ports... i THINK...
i know for p's you need new headers

reg. gt40s give you an 8.8-1 comp ratio.... and you can use n e set of headers...

im using reg. gt40s

Dave5point0

P's = requires different headers and not to much of an advantage i don't believe (although there may be a little comp difference)
edit: whoops, dime beat me to it

FLcracker9

The P heads have turbo-swirl combustion chambers, higher compression ratio and smaller valves. Even with the smaller valves, they flow better than the GT40s because they burn more efficiently, and scavenge the exhaust gases better. Because of the different combustion chamber, the Ps have the spark plug located in a different position than the GT40s, therefore requiring a special header (MAC makes headers form the Ps). Some people here say you can use regular headers if you use 90 degree boots onsome of the plugs to clear the headers. I think GT40s are more popular to modify, but in stock form, the Ps make more power.

coony278

thanks for the replies guys , I know the headers will bolt on the head , I have a set off that I bolted on to the GT-40p's , and with the right spark plug boot it shouldnt be a problem.

However , here is another question, Are the GT-40p heads worth putting bigger valves in and porting ? How big of a valve will fit in these heads ? Combustion chamber does look small and may not be room for 2.02 and 1.6 valve.

Or if this was you would you sell the gt-40p's and just get aftermarket heads ??? thanks

Chad

Mustangkiler

biggest you can put in is 194 intake and 154 exhaust

FLcracker9

Here's a pretty good article on home porting GT40P heads, along with installing larger valves. It includes some pictures and flow numbers.

http://www.diyporting.com/gt40p_home_porting.htm

coony278

Thanks that is a very good article . I think I will use the GT-40p heads. I have ported alot of heads over the years. And have always had good luck porting them. I will not have as much money in my heads as the guy in the article since my heads was free


Chad