2020-03-20 - GT40/GT40P & Cobra/Explorer Intakes
I have previously cleared this with Mike C so I want to re-clarify that for a 1993 Cobra engine the Explorer/Cobra/Lightning intakes are considered the same and GT40 and GT40P heads are considered the same.
The previous reply from Mike, "The GT40/GT40P heads are the same. The Cobra/Explorer intake is the same."
The data for the intakes can be seen here on an American Muscle site: http://lib.americanmuscle.com/files/contentgenerator/f ... epower.jpg
It is common knowledge that all three intakes have identical internals and any hp gain is likely due to Ford's loose manufacturing tolerances.
With respect to the heads there are minor differences documented on the same site but again hp differences are negligible. The web site: https://www.americanmuscle.com/cylinder-head-upgrades.html
With the relevant portion being: "Furthermore, there is said to be slightly different chamber volumes. GT40 combustion chambers are slightly larger, with volumes ranging from 63-66 cc. The Explorer/Mountaineer heads (GT40P) are somewhat smaller, measured between 58-61cc chamber volume. Thus, GT40P cylinder heads may give a small bump in compression.
Finally, the last difference between the two are valves. Both have 1.84" intake valves, but the GT40 has a 1.54" exhaust valve whilst the GT40P cylinder heads have a slightly smaller one at 1.46".
GT40 vs GT40P, which are better?
Really, when you get down to it, neither head is any measurable difference better than the other. The GT40P does have a slight edge over the GT40 cylinder head because of its smaller chamber volume.
The smaller combustion chamber can net a bit more compression, but only marginally. Flow data shows them to flow within a few CFM (cubic feet per minute, more CFM is better) of each other.
Conclusion: "one is not downright better than the other. If you're stuck deciding between the two, go with whatever is available and at a better price."
We will consider the GT40 and GT40P heads the same.
We will consider intakes from a Cobra or Explorer the same.