Stock Fox Body Mustang Head Options
Like previously mentioned, the E7TE heads (stock heads on 87-93 5.0L Mustangs) don't flow enough air. They also weigh quite a bit, as they are cast from iron. Ways to improve them are:
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, polishing the chambers are all part of the process. Porting can yield some results. However, done on these E7 heads, even an A+ job may only yield a 30HP gain. 30HP is nothing to sniff at, except that porting is very expensive. Unless you do it yourself, you will have to pay a professional (the general consensus is they usually charge an arm and a leg) to do it for you. At the end of the day, it isn't really 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 really 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.
Aftermarket Fox Body Cylinder Head Options
The aftermarket offers astonishing improvements over stock heads. 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.
Edelbrock: 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 from their range of products, 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 and may need new ones as the supplied ones are only for very mild cams (stock HO cam is too much). 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 issue.
Ford Racing: 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 this horsepower adding 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 lift and a commanding 65HP gain, these are some solid heads. These GT40Xs are comparable to the Edelbrock Performers - similar pricing and similar performance. They are a great step up from the stock E7s. Again, very good for a mild street/strip build supporting between 300-350HP, depending on what other parts are on the car.
Trickflow: Trickflow, as its name implies, does use tricks to increase airflow on its 5.0L compatible Twisted Wedge 170cc head. By far this is the most popular choice among Mustang enthusiasts. However, it is also the most expensive. But as some would say, you have to pay to play. Trickflow Twisted Wedge heads use dark magic to make power. 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 come by 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.
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 by these aftermarket heads as cast. Or, 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 as 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.