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GT40/GT40P Heads and Ford Explorer
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GT40 and GT40P heads are probably the best
factory production small block Ford heads.
GT40 and GT40P heads
have line designations on the end of each casting. 3 lines on the GT-40
and four lines on the GT-40P. GT40 heads are found on 96 and early 97 V8
Explorer/Mountaineers as well as 5.8L Lightnings and 93-95 Cobras. GT-40P heads are
found on the 97½ and newer 5 liter Explorer/Mountaineer V8s.
The 5.0 explorer
throttle body is 65mm and will fit a
Mustang but you must swap out the throttle shaft and arm from the Mustang
GT40 and GT40P share similar intake runner volumes at about 145cc compared to E7's 124cc. All accessory
bolt locations and valve train geometry are the same between the GT40P and
1.85/1.46 valves compared to 1.85/1.54 for the standard GT-40. The
GT40P exhaust port is redesigned and is more efficient than the standard
GT40 which is the reason for the smaller exhaust valve. There is room for larger valves but
keep in mind going larger on
the intake side will cause clearance problems with the spark plug boss.
GT40P combustion chambers range from 59cc to 61cc based on factory
machining tolerances. GT40 combustion chambers are roughly
Small emissions-type bump in exhaust port similar to E7TE casting but
not as large. This bump is in the center on the port roof right at the
exit and can be easily removed.
No thermactor holes in the GT40P heads
Intake port dimensions are close to a Felpro 1250 gasket.
GT40P can use stock pedestal mount rockers.
On GT40P heads the spark plug hole is moved down and rotated out which
puts the electrode closer
to the center of the combustion chamber. providing a better burn, reducing
emissions and increasing efficiency. The GT40P does not use standard 5.0L
spark plugs. GT40P uses Motorcraft AWSF-32C.
Standard unequal length shorty headers won't work because of the GT40P
spark plug location. MAC offers a coated GT40P-specific shorty and Ford
Racing offers a set of stainless shorties that work. Stock Mustang headers
work also. Most equal length shorties will not work. BBK
equal length shorty headers have been known to fit. MAC, Hedman and BBK
full length 1 5/8" headers fit. Some full length headers require
minor clearancing on some primary tubes but is not a big issue.
Spark plug wires with 90 degree boots are recommended with all headers.
TFS-2500100 valve spring upgrade kit
comes with 1.47 springs, retainers, locks and valve seals.
spring will NOT fit a GT40 head w/o machining to the inner part of the cup
but a basic 1.46/1.47" single spring will fit, There is an inner "lip"
that is about .060" tall that most likely will have to be machined flat.
You can also go a step further machine the guide too and use the 1.300"
LSX dual springs.
Gasket matching does not net any significant increases in airflow on these heads. These
heads are sensitive to the work in the bowl area (including the guide
boss) and the short turn. A good 5 angle valve job is a good idea too.
If you are not a head porter, don't try to be one. P heads are easy to screw up
so leave the work to a professional. If you want to get carried
away, a 1.94 intake valve and 1.50 exhaust valve will help flow a bit.
Typical peak flow numbers on a well done set of P heads is about 230 cfm
on the intake and 160 cfm on the exhaust at .500 lift.
GT40P heads are similar to GT-40 heads
with the biggest
difference being the P-heads feature a revised spark plug
angle which extends the plug into the combustion chamber, putting the flame
front close to the absolute center of the chamber, resulting in a smoother
combustion process. P-heads have a smaller combustion chamber (approximately 59cc), which
will increase the compression ratio over E7TE heads.
The following modifications must be
made for Explorer intakes to bolt up to a 1987-1993 5.0
1. Lower Intake:
Explorer intake has no hole for the ACT (Air Charge Temperature) Sensor. You
have two options here: Drill and tap a hole for the sensor or relocate the
You'll have to swap over all related hardware from your stock intake (temp
guage sender, coolant lines, etc)
lower intake itself doesn't have a return port for the EGR coolant flow, so
you have two options: Drill and tap for a return port or block off the supply
port on the coolant lines.
2. Upper Intake:
the four throttle body studs from your stock intake onto the Explorer intake.
the back of the stock intake, there are three vacuum ports (fuel pressure
regulator, Emissions, and vacuum tree). At the back of the Explorer intake
there are only two. You can use T or Y connector to split the ports.
of the other vacuum ports on the intake are a little too long, so using a
cutoff wheel, trim them to the desired length.
an Explorer 65mm Throttle Body for Use on Mustang:
The Explorer TPS is not the same as the Mustang.
It uses a different resistance range and has the two bolt holes set slightly
wider apart - you'll have to drill the stock Mustang bolt holes larger to get
them over the 65mm TB mounting holes.
The tab at the end of the TB shaft that slips into the TPS is also a little too
long for the stock TPS - it needs to be ground down to the same height as the
The 65mm TB has the boss for the 90° hard line elbow line that runs from the oil
fill neck to the stock TB but it is not drilled nor does it have the elbow. You
cut the boss that the stock one is pressed into deep enough with a thin cut-off
abrasive blade so you can crack the side of the boss away, making removal of the
90° elbow easier. Then use a uni-bit step drill with 1/4" long step sections to
drill the new hole in the 65mm TB boss to accept the elbow. Then inserted it and
use epoxy to hold it in place.
The throttle linkage ball is also "clocked" in the wrong position for the
Mustang. Cut the linkage off an old 60mm TB and used it. The shaft is split at
the end and when the factory slides the throttle bracket and return spring on it
during assembly, they press the split end of the shaft and crush it onto the
slot in the throttle bracket. Use a small abrasive wheel and grind the pressed
halves of the shaft off so you can pry the throttle bracket off. If you
don't grind the stock bracket too bad and the slot is intact, it will slide over
the Explorer pressed shaft halves and create an alignment that is correct. Epoxy
or some spot welds can be used to hold the cut off 60mm bracket onto the 65mm