GT40p???

bitem · Post by **bitem** » Wed Nov 01, 2006 7:42 pm

So whats up with th GT40P heads? I have a set of aluminum GT40s and the valves a reletivly small compared to most but the low comp ratio is good for running the cheapy gas. Next time around I will get the Twisted Wedge heads. They make a couple of sets with the larger valves and the large combustion chambers now. I haven't read up on them I have just noticed that a lot of you guys are running them and with the header intererence there must be a good reason.

Dave · Post by **Dave** » Wed Nov 01, 2006 8:15 pm

They'e cheap and come with the Explore engines, said to be the best cast iron heads that Ford has made. Low buget, no problem if you can find headers. Been told that the old Hi-Po headers will work. I'd got for a more performance head my self. The heads you've got are better.
Dave

MalcolmV8 · Post by **MalcolmV8** » Wed Nov 01, 2006 8:39 pm

Yup GT40P comes with the Explorer motors which is why I'm using them on my daily driver. They have a different spark plug angle and make headers a bit of a nightmare. Your choices are greatly reduced, but they will work.

plowboy34 · Post by **plowboy34** » Wed Nov 01, 2006 9:23 pm

Hey Dave, are you talking about the old 289 HIPO manifolds? If you are they will not work on the "P" heads. I had a set and checked to see if they would work and they would not. I had heard the same thing so I checked it out.

cgrey8 · Post by **cgrey8** » Wed Nov 01, 2006 9:27 pm

There used to be a website that detailed out the cast iron GT40 vs GT40p however it doesn't seem to be up anymore. Here's the thread entry where I detailed out the differences between the two.

Mustang to Explorer

For a review of the differences between the aluminum GT40 and GT40p heads, you can go to the AFR website and see flow and performance measurements done by MM&FF:
MM&FFs Ultimate Guide to 5.0 Cylinder Heads, Part 1
MM&FFs Ultimate Guide to 5.0 Cylinder Heads, Part 2

Towards the end of the 2nd article, you can get an overview of both flow and performance of the various heads they tested. The aluminum GT40 heads clearly outflowed the GT40p heads as well as gave higher MAX hp and torque values. However look at the average HP/torque numbers. The GT40 heads are not that far ahead of the GT40p heads. THAT's why they are so popular amongst the "budget" builder. There's also a GT40x casting, but I don't know anything about them.

But there's still no substitute for professionalism at its best. Holley, Edelbrock, TW, and AFR are the clear dominators in the SBF head arena with AFR leading the pack. If I could afford it, I'd have a set of AFRs. Those heads are just plain awesome from idle-to-redline.