Are there different types of GT-40 heads?

And if there is which ones are better for 289/302 use in a Mustang.

I have seen some listed lately as GT-40P heads and others I believe were listed as GT40T...

Am I correct in assuming there are different types and if so what's the difference (i.e. is one better than the other?)

 

Yes, there are. They basically use 351W port castings with 302 sized combustion chambers. They flow much better than stock heads, so if you can find them for cheap, they can make a great bolt-on power upgrade. There is the compression ratio drop to factor in, though. You can always port-match your exhaust and pick up a lot of the flow that you're losing due to crappy exhaust port castings.

GT40P heads are GT40 heads with fast-swirl combustion chambers, to allow a faster burn in the chamber for more power. They come on They have altered spark plug angles, which makes fitting them into classics a nightmare. There are only two companies I'm aware of that make classic headers specifically for P heads, and they're both very pricey (but very high quality). Some long-tube headers may fit, but there's no guarantee, even between different headers from the same manufacturer.

GT40X heads are aluminum GT40P heads without the altered spark plug angle. Nifty, but not worth what you'd pay for them. You'd be much better off buying aftermarket heads.

 

I was just curious because there is a set of P's for sale locally along with a 302 but I thought I had read or heard P's are not a good idea.

Ran across a guy a few weeks ago that had a set of ported GT-40's and he was supposed to send me a picture but seems to have fallen off the face of the earth so don't know....I don't believe his were P's though if I am remembering correctly.

 

Now I recall where I had read something about GT40T heads....duhhh.....man am I a scatter brain some days.....

I have been talking some to a local machinist guy that builds engines and he was suggesting that if I wanted him to build me something he could build a 302 with GT40-T heads with 1.94"x1.50" valves and a street performance cam, with spec's of 214/224`@.050" amd .472" lift. Add on a 4 bbl plus intake and you certainly would be better than what I have performance wise.

Just haven't gotten him to give me a straight answer regarding what sort of HP he is thinking this set up might put out....

 

That's not exactly what I'd call a 'performance' cam. You can get more lift out of that.

 

If I go that route I will keep it in mind and mention it to the guy....that was his recommendation.

Cam selection makes my head hurt to be honest and that is in large part why I have also been considering just going with a top end kit.