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Upgrading Fox Body Cylinder Heads

Written By: Connor MC

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It's no secret the old-school 5.0 Foxbody motors are under powered in today's age. It's also well-known how easy it is to wake up your 5.0 with a few engine modifications. Stock Foxbody cylinder heads have very poor airflow, but luckily the Mustang aftermarket has a ton of upgrades available.

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To squeeze some more ponies out of your Fox Body Mustang, upgrading the cylinder heads can lead to some substantial results. This guide contains a Fox Body cylinder head flow chart and information on available upgrades, ranging from the stock E7 heads to fully prepped, CNC machined aluminum beauties.

American Muscle

A Matter of Airflow

The 5.0 equipped Mustangs in their day (1987-1993) were nothing to shake a stick at. However, come the 21st century, the meager 225HP output by their mighty 50.L V8's is way too low compared to modern standards. Luckily, despite the age of these cars, ongoing research and experimentation by aftermarket companies have yielded some impressive new parts to really waken up that low-on-power 5.0. It's common knowledge a major restriction point, from a power perspective, is found within the factory-cast E7TE heads that originally came equipped on the Foxbodies. They just don't flow enough air into the engine. They also weigh quite a bit, as they are cast from iron. This guide presents the best options to upgrade your Fox Body Mustang's cylinder heads.

1993 Foxbody Set-Up for Drag Racing

Porting Fox Body Cylinder Heads

Porting heads involve using a rotary tool (dremel) and a burr to restructure the passageways to optimize air flow through the cylinder head. Remove unnecessary casting material, smoothing out imperfections, and polishing the chambers are all part of the process. Porting these E7 heads, even an A job, may yield a 30HP gain. 30HP is nothing to sniff at, except porting is very expensive. Unless you do it yourself, you will have to pay a professional to do it for you. At the end of the day, it isn't logical to spend $500 for someone to port these iron heads for a measly 30HP. Of course, you can do it yourself. Many enthusiasts have. With some dedication and careful work, you can port it yourself. Alas, it is also just as easy to hamper performance as it is enhance it if you are a beginner. Iron is also somewhat difficult to work with.

Replacing Fox Body Cylinder Heads

At the end of the day, E7 heads just aren't worth the money to improve. Aftermarket options have come a long way. They offer incredible power improvements over stock AND room to grow. In comparison, E7s are nearly maxed out in stock form. Read below to get an overview of what the aftermarket has to offer.

Valvetrain Components Exposed on a Foxbody Mustang

Aftermarket Fox Body Cylinder Head Options

The aftermarket offers astonishing improvements over stock heads, for both forced induction and naturally aspirated applications. Some well known names are Edelbrock, Trickflow, and of course Ford's own performance branch, Ford Racing. Benefits from these aftermarket heads are simple - better design, lighter weight, more power! All of these heads are of superior design and quality. They also are all made from aluminum which gives a significant weight savings over the stock cast-iron heads. Furthermore, they are all a direct bolt-on! No fiddling or special modifications necessary to have them fit on your 5.0L roller block.

Vortech V3 SI-Trim Mustang Supercharger Installed
Centrifugal Supercharger

Edelbrock Heads

Edelbrock has several models for those considering upgrading their cylinder heads on their 5.0L V8. The E-Streets and Performer heads are the most popular choice because of their range of performance options, with the former being their lowest entry option. Both offer an aluminum design, 170cc intake ports and valve sizes. The E-streets are intended for those with the budget in mind and subsequently do not offer the same amount of performance as the Performers do. As part of a cost saving procedure, the E-Streets use weaker valve springs designed for very mild cams. Edelbrock's Performer heads are a little more robust. Both Edelbrock models are considered entry level aftermarket heads for a mild street build, with a power range from idle to 5500 rpm. With the right combination, these heads can support 300-350HP (flywheel) without an issue.

Edelbrock Performer Cylinder Head for 5.0L Foxbodies
Edelbrock Performer Cylinder Head

Ford Racing Heads

Ford Racing has a longstanding history with aftermarket parts. Specifically, their latest generation GT40 aluminum cylinder heads. Based off the original and incredibly popular GT40 iron head (from the 90s), Ford has continued to improve the design over the years. Today their efforts come to fruition in the GT40X Turbo Swirl 178cc cylinder heads. Claiming a hefty 240 CFM of flow at 0.550" of lift and a commanding 65HP gain, these are some solid heads. These GT40Xs are comparable to the Edelbrock Performers - similar pricing and similar performance. Again, very good for a mild street/strip build supporting between 300-350HP depending on what other parts are on the car.

GT40X Aluminum Ford Racing Foxbody Cylinder Head
GT40X Aluminum Head

Trickflow Heads

Trickflow, as the name implies, does use tricks to increase airflow on the Twisted Wedge 170cc head. By far this set is the most popular choice among Mustang enthusiasts. However, it is also the most expensive. As some would say, you have to pay to play. Trickflow has rotated and moved the valves from their traditional position to a position atop the cylinder bore. What does this mean to you? This voodoo supposedly optimizes and increases airflow and thus power. Like the others, these heads are great for a mild street or track build. 300-350HP is not hard to get to with these heads. However, they do have one extra trick up their sleeve. In my opinion, the Twisted Wedge heads have the greatest amount of potential, i.e: plenty of room to grow if you need more power.

Trickflow Twisted Wedge Foxbody Cylinder Head
Twisted Wedge 64CC Head

Fox Body Cylinder Head Flow Chart Comparison

All numbers are issued by manufacturer. Measured in CFM
Lift (inches)0.1000.2000.3000.4000.500Average Flow (CFM)
Stock Ford E7TE48
Edelbrock Performer72
Ford Racing GT40X60
Trickflow Twisted Wedge 17062

Here we have a comparison between some of the leading performance cylinder heads available for Foxbody Mustangs as well as the stock Ford E7TE heads. As you can see, Edelbrock, Ford Racing, and Trickflow all produce competitively performing heads, each having their own advantages anddisadvantages. Choosing the right cylinder heads for your Fox Body build is essential and will help you determine the overall direction for the rest of the car.

Choosing Aftermarket over Stock Fox Body Cylinder Heads

As you can see from the flow numbers, any of these aftermarket aluminum cylinder heads will really wake up that 5.0L slumbering beneath the hood. Furthermore, they are available in different stages and packages. For example, you can buy these aftermarket heads as cast. If you prefer some more power and at an added cost, you can opt to purchase a CNC machined version which will have better airflow over the cast version. Each head can come equipped with different spring packages, smog equipment provisions, etc. There really is nothing that Edelbrock, Ford Racing, or Trickflow has left out. Extra power certainly can be squeezed out of the stock E7s, but with the design and technology implemented within the modern aftermarket heads they really are the best choice.

Flowing More Air From the Intake To The Exhaust

Stock throttle body, while adequate for stock applications, is not the end all be all of throttle bodies. There are many aftermarket applications that outperform the stock throttle body. The stock unit is limited by size, something an aftermarket throttle body can fix. When changing heads, camshaft, intake manifold, etc.

It is always a good idea to change the throttle body. Retaining a stock throttle body size while upgrading everything else creates a larger bottleneck at the throttle body. Also, the price of the throttle body is quite cheap when compared to heads, it is a small price to pay for a substantial benefit.

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