GT40 Irons - Is there a difference?

[TheBocSez]

I was wondering if there is a difference between the GT40 Iron head found on a Lightning as opposed to those found on a 93 Cobra?

The only I could think of would the the possible need for headbolt bushings on the one from the Lightning. Any other differences?

I have access to some that are close by from a Lightning or some I can buy and have shipped from a Cobra.

Just trying to see which will work with my car with the least amount of trouble. BTW, it have a 91 LX.

Thanks!

 

[notchback]

nope...same head

i've heard that early explorer heads are real 40's and not "p"'s but i have never spoken to anyone who actually knew...just heard it around

 

[IntenseBlue]

I think the lightnings had 2cc bigger combustion chambers. Not positive though. The Cobras and Lightnings weren't Ps. The 97-up 5.0 explorers had Ps.

 

[SeventyMach1]

The 97-up 5.0 explorers had Ps.

But not all '97 Explorers/Mountaineers had the P head. They switched from GT40 to GT40 P midway through '97, so some of them do, some of them do not. My '97 Mountaineer heads are regular GT40's because they're early '97's.

 

[rd]

I have a set of SVO GT40 irons and a set of Lightning GT40 irons. Both have the bigger head bolt holes. The Lightning set had the production valve spring rotators on the exhausts, which I changed out to Comp Cams springs, retainers and keepers. Ohterwise I dont think there is any significant difference. I have one set on a 68 block and one set on a 79 block. Work fine.

 

[87MustangGT5.0]

Is there a big difference between the P and the non-p?

 

[IntenseBlue]

P's require different headers, but they make more power. Nothing huge, though.

 

[SeventyMach1]

P's require different headers, but they make more power. Nothing huge, though.

Uh, no, P's DO NOT necessarily require different headers!!! I know many guys that run them with regular headers. You may have to modify 1 or 2 spark plug boots (to 90 degree boots) .... but regular headers will work just fine. And yes, the P's will make just a little more power.

 

[TheBocSez]

Cool, thanks for the info guys. Since the Lightning heads are cheaper, closer, and more recently machined, Im going with those. Thanks again.