GT40 vs GT40P Who has smaller chamber volume with more compression

GT40 vs GT40P, which cylinder head is better? The GT40 and GT40P are two different sets of castings for four-cylinder Explorer/Mountaineer heads. The GT40P has smaller chambers, so it is a bit tighter than the GT40, although we do not recommend using the GT40P heads on a high compression build. The flow numbers for both heads are the same.

GT40p Heads

What is the difference between GT40 and GT40P heads?

Explorer/Mountaineer heads (GT40P) also feature smaller ports, with valve diameters of 1.84 inches (46.73 mm) as similar to the GT40’s 1.54 inches intake and 1.88-inch (39.11 mm) exhaust valves.

gt40p heads specs

The GT40’s port design is a combination of rectangle and oval shapes for the intake ports and straight sides for the exhaust ports. The GT40P heads use circular intake ports with rectangular exhaust ports, which may allow more airflow into the combustion chamber.


Head TypeIntake PortCombustion ChamberIntake ValveExhaust Valve
GT40 – Explorer145cc65cc1.851.54
GT40 – Cobra145cc61cc1.851.54


The differences between the two heads are subtle, but important. The GT40P head is cast with slightly smaller combustion chambers than the GT40 head, but the valve size remains the same.

The GT40P head also has a slightly different spark plug positioning than does the GT40 head. These changes may result in a small bump in compression ratio when using a GT40P cylinder head on a stock short block.

302/347 Stroker SBF Dish Top E Series Forged Piston Set.030

302/347 Stroker SBF Dish Top E Series Forged Piston Set.030

YEHAM 3″ Engine Piston Ring Tool & Piston Ring Pliers with Adjustable Screws

YEHAM 3" Car Engine Piston Ring

What vehicles have GT40 intake?

  • 1993-1995 Mustang Cobra | Part# F3ZE or F4ZE
  • 1996-Mid 1997 Ford Explorer & Mountaineer SUV | Part# F1ZE-AA
  • 1993-1995 Ford F-150 Lightning | Part# F3ZE or F4ZE
  • 1993-1995 SVT Cobra Mustang and 1993-1995 SVT Lightning – GT40 heads
  • 1996-Mid 1997 Ford Explorer & Mercury Mountaineer SUV –GT40 heads


  • Mid 1997+ Explorer/Mountaineer SUV Models | Part# F77E-AA

GT40p vs GT40 Heads and intake

 What engines came with GT40 heads?

  • Trick Flow Cylinder Head Twisted Wedge 11R 190cc Intake 2.055/1.60 Valves Dual Springs 56cc Chambers Street Port 289/302/351W
  • AFR Cylinder Head Aluminum 220cc Intake 7/16″ Stud 72cc Chambers Without EGR Pair 289/302/351W.

The GT40 heads are a little bigger. This gives them a slightly better flow and build quality. The GT40P heads have more aggressive camshafts, which will give you slightly more power. The GT40P heads also have smaller valves that can help the engine breath better.

gt40p intake Mustang

The GT40P has a higher number of intake ports than the GT40, thus, it allows for the use of larger valves. The shape of the combustion chambers are pretty much the same on both heads, but the GT40P is smaller in size. This leads to increased compression because there is less room for a charge to fill. The valves do not have as much lift so they cannot flow quite as well as the GT40 valves but they do flow better than stock Explorer heads.

The new GT’s body is made of aluminum, which has become more prevalent in automobiles, but it is its engine that makes the GT40 stand out from all other Ford products.

The GT40 employs a 7.0-liter V-8 engine — a big block engine — that produces 500 horsepower at 6,500 rpm and 487 foot-pounds of torque at 4,500 rpm. The engine was built by the company’s Special Vehicle Team (SVT) using an aluminum block and heads with four valves per cylinder and dual overhead cams. It also features forged steel connecting rods with titanium bolts and a lightweight cast aluminum crankshaft.

In addition to its big displacement V-8 engine, the GT40 also has racing suspension and brakes designed for track work as well as high speed cornering capabilities. Testers have recorded 0 to 60 mph acceleration in less than 4 seconds and quarter mile times in the low 11 second range.

What is the difference between a GT40 and GT40P engine?

The GT40P cylinder head is a very common street performance part. It has been used by Ford Racing for many years as the foundation for their high-performance crate engines. While the GT40 cylinder head is no longer a stock production item, there are still thousands of them out there in street and race applications.

On the other hand, if you are using a stroker crank in combination with a GT40P cylinder head, it will be necessary to use valves of larger diameter to maintain proper quench clearance.

This may reduce peak combustion pressure and increase exhaust gas reversion because of incorrect valve-to-piston spacing (valve shrouding).

Finally, increasing the height of the piston dome (by using an aftermarket flat top piston) will also have an adverse affect on combustion pressures due to reduced quench area.

How much horsepower do GT40P heads add?

So, how much horsepower can you get out of GT40 heads? It’s also important to note that while GT40P is only making a 25 hp claim, you may see more or less power depending on the combination of parts you’re using in your engine.

The GT-40P was designed for increased airflow at high rpm, but to take advantage of this feature you’ll need to use a camshaft with lift and duration specs greater than those of the flat tappet hydraulic camshaft that came with your engine. This could result in increased valvetrain stress on both the cam and rocker arms, so a more durable replacement is recommended.

The stock cast nodular iron cam is a good choice, as are aftermarket roller cams with similar specs. The most important thing is to match the intake valve size (2.08 inches) of the GT40 with an exhaust valve size that matches your intended application.

What’s the difference between Ford GT and GT40?

The GT40 was a high performance automobile produced in the United States as a more powerful, larger, and improved version of the Ford GT.

The GT is closely related to the original GT40; the roofline and windshield are nearly identical to the earlier car. However, several significant changes were made to modernize the car:*

 The chassis was updated with a lighter, all-aluminum design and shortened by 40 inches while the overall height was increased by 4 inches (101.6 mm).*

 The body of the car was radically altered from that of the original GT40; rather than a fully integrated body, the body of the GT is made of aluminum with composite panels riveted onto it.

 The engine compartment is larger than on the original GT40.

Back with history
A primary goal of ours in building this GT40 replica was to mate the GT40P heads to the 302 Windsor block. We didn’t want to use the stock GT40P intake manifold, either. Many years ago, we built a similar engine but with a Edelbrock Performer RPM intake manifold and a small-block Chevy oiling system.

GT40 heads vs stock

The most important thing to understand about a GT40 head is that the ports are very small. If you port them they will flow well, but they will not flow as well as an LS1 head because the intake valve is smaller and the ports are just not big enough to match a LS1 head.

Tuning is everything with these heads. The cams you use must be around .600″ lift or less. If your cams are too big it will kill your low end and leave you high in mid-range. Also, if you choose to use aftermarket heads instead of GT40s then choose the highest flowing heads you can find with steel valves and at least 1.94 intake valves.

Are gt40p heads aluminum?

Yes, the GT40P are aluminum. The cylinder walls are similar to those in a cast iron head, but the spark plug holes are different, and the spark plug boss is offset. The GT40X and GT40Y are aluminum as well, with slightly different combustion chamber shapes.

gt40 vs gt40p mustang


Is the GT40 a Mustang?

The Mustang is a modern interpretation of the original GT40

How do I identify my gt40/gt40 heads?

Check inside the head casting “GT” or “GT40P” or a 3-bar ||| (GT40) sign or

And for (GT40P) you will see 4 bar |||| stamped on the side of the head.

What’s the best Cam for a GT40P?

Cobra Crane 1.7 Roller Rockers is the best cam for 1993 Ford Mustang

What year did the Ford GT40P cylinder head come out?

In 1997 the Ford GT40P cylinder head come out.

How much horsepower can you get out of GT40 heads?

25 hp can you get out of GT40 heads.

How much do GT40P heads flow?

Runner Volumes: 155cc int. est. 55cc exh.


So, GT40 vs GT40P which one is better? Both the GT40 and GT40P heads have been used on many different applications. The GT40 heads are a bit more versatile, working with the 5.4 and 6.8, while the GT40P (Explorer/Mountaineer) heads will only work on the 6.8 due to an interference issue.

Both have very similar valve sizes, but the GT40P head has slightly larger combustion chambers for a small bump in compression and better flow.

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