MustangWorks.com : Ford Forums - View Single Post - how to tell what kind of GT-40 heads

red82gt · 03-07-2002, 02:29 PM

on the front and back of the head:
3 vertical lines=GT-40
4 vertical lines=GT-40P

There will also be a "GT" stamped near the #1 spark plug hole.

There's lots of debate as to which are better, the main differences are that the P head has a smaller combustion chamber and a 1.46" exhaust valve whereas the regular GT-40 has a 1.54". The spark plug angle is different for the P heads and makes some headers not fit. I've seen tests that had the non P head outflowing the P head, especially on the exhaust side but there are people on this board who will disagree with me.

Either way, they're a good deal and you'll pick up a ton of power over the stockers.

03-07-2002, 02:29 PM	#3
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,514	on the front and back of the head: 3 vertical lines=GT-40 4 vertical lines=GT-40P There will also be a "GT" stamped near the #1 spark plug hole. There's lots of debate as to which are better, the main differences are that the P head has a smaller combustion chamber and a 1.46" exhaust valve whereas the regular GT-40 has a 1.54". The spark plug angle is different for the P heads and makes some headers not fit. I've seen tests that had the non P head outflowing the P head, especially on the exhaust side but there are people on this board who will disagree with me. Either way, they're a good deal and you'll pick up a ton of power over the stockers. __________________ 393W: AFR 205's, hydraulic roller, TKO600.