ChampCar Endurance Series

ChampCar Tech Desk

Official channel for ChampCar technical questions, interpretations, and VPI requests.

Before you submit a ticket

The Tech Desk is for rules clarifications and technical questions. It is not a post race tech line, a place to protest results, or a place to fish for how other teams built their cars.

Most questions can be answered by reviewing the current BCCR Rulebook. Please read the applicable section before submitting a ticket.

If your question is already covered clearly in the BCCR, your ticket may simply be answered with a reference to the rulebook section.

VPI request checklist

For all Vehicle Performance Index (VPI) requests you must include:

  • Year, make, model, and trim level
  • Engine size and engine horsepower
  • Drive type: FWD, RWD, AWD, or 4x4
  • Transmission type: automatic or manual
  • Car weight and all factory options that affect performance
  • A link to the vehicle on automobile-catalog.com or another site with full specifications if it is not listed there

Requests that do not include all required info and research will be denied without review.

Open BCCR Rulebook Tech Desk Home
ChampCar ChampCar Tech Desk Knowledgebase Engine & Cooling
2020-03-20 - GT40/GT40P & Cobra/Explorer Intakes
Suggested knowledgebase articles:

2020-03-20 - GT40/GT40P & Cobra/Explorer Intakes

Q.
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."


A.
We will consider the GT40 and GT40P heads the same.
We will consider intakes from a Cobra or Explorer the same.


Verified by TECH 2024

Was this article helpful? Yes | No

Article Details

Article ID:
117
Category:
Engine & Cooling
Date added:
2020-03-20 15:40:57
Views:
20,801
Rating (Votes):
(425)

Related articles