Muscle Mustangs & Fast FordsHow To Engine
Ford Mustang Edelbrock Cylinder Heads Install and Test - Serious Performers
Swapping Edelbrock heads for 78 horsepower.
The name Edelbrock conjures up all manner of performance components, and for good reason. Enthusiasts have relied on Edelbrock performance components for over 65 years. Tucked in with all the intake manifolds, camshafts, and exhaust systems are a wide variety of cylinder heads. Edelbrock offers everything from mild performance bolt-on replacement heads to CNC-ported race heads. Much to the delight of Ford fans, Edelbrock recognized the importance of the 5.0L Mustang market and began offering a number of different aluminum cylinder heads to replace the stock cast-iron 5.0L heads. Our testing for this article centers on its 50-state-legal aluminum Performer Ford heads.
The California-based company offers a three-tiered approach to Ford performance cylinder heads. Edelbrock fans now recognize that the designations Performer, Performer RPM, and Victor Jr. indicate different performance levels. This approach is a wise one, as not every builder has maximum performance (and associated trade-offs) in mind. If one head was right for every application, then all of the manufacturers would zero in on a lone design and we would be left with no cylinder-head choices.
Before getting to the impressive power numbers, it is important to understand what part the heads play. Like any internal combustion engine, the Ford 5.0L 302 produces power by processing air and burning fuel. We use the word processing to designate the fact that any airflow that goes in must also find its way out. The more air it can process, the more power it will produce. One way to increase the amount of airflow is to increase the size, or displacement. Bigger-bore pistons and longer stroke cranks help draw in and push out more air. That is why bigger motors make more power than smaller ones. Another method is to force air into the motor by some form of forced induction. The final method is to reduce restrictions inherent in the basic motor, or improve its ability to breathe. For this article, we will concentrate on this latter method.
Improving the ability to breathe means removing (or greatly reducing) any component or design that may hinder the ability to process air. Starting from the exhaust forward, this means providing the motor with a free-flowing exhaust system. With the exhaust taken care of, we can turn our attention to the intake. The intake tract for a carbureted motor (like out test mule) begins with an air filter, but the main component is the carburetor. Always select a carburetor sized for your application, and don't be afraid to ask a pro if you are unsure. The intake manifold is next, and it should be chosen based on flow and the intended operating rpm. The manifold should work with the cam timing to effectively determine the power curve of the motor. The final elements in the equation are the cylinder heads.
A simplistic overview is that the cam timing and intake manifold determine where the motor will make power and the head flow determines how much. Of course, things like compression, cubes (displacement), and carburetion all play a part in this dynamic equation, but without a good set of cylinder heads, your combination will likely fall on its proverbial face. While maximizing cylinder-head flow is critical to optimum performance, it is every bit as important to remember that bigger is not always better. Remember we said the engine is a dynamic equation? Just like the cam timing and intake design, the head port volume (and airflow) must be sized to operate effectively in a desired rpm range. Installing a set of wild NASCAR Yates heads on an otherwise stock 5.0L 302 would be a monumental waste of time. The rest of the components in the stock motor (intake, cam and exhaust) would sign off well before the head started to reach peak efficiency. The result would likely be a lazy motor that makes less power than the stocker.
For this reason, Edelbrock decided to instrument the tiered approach to cylinder heads, as well as intakes and cams. Obviously, it recognizes that a mild 302 requires different cylinder heads than a wild 408 stroker. For our test, we selected heads from the lowest of the three tiers, namely a set of 50-state-legal Performer Ford heads (PN 60329). Edelbrock also offers a set of bolt-on replacement Performer heads for a 5.0L 302 (PN 60289), but we opted for the heads set up to accept adjustable rockers. The Performer 5.0/5.8L heads were set up to accept bolt-down rockers, but we liked the freedom of the adjustable rockers, not to mention not having to deal with rocker shims.
The Performer heads featured A356-T-6 aluminum construction to reduce curb weight, compared to stock cast-iron heads, and a 1.90/1.60 valve combination. The Performer heads are also available with 2.02 intake valves (retaining the 1.6 exhaust valves) under PN 60349, but we opted for the smaller valves. Care must be taken with the larger valves as they reduce piston-to-valve clearance. Our Probe Racing pistons were equipped with generous notches, so clearance was not an issue.
In addition to the 1.90/1.60 valve combination, the Edelbrock Performer aluminum heads were set up with a spring package suited for our hydraulic roller cam. The spring package produced 125 pounds of seat pressure and 290 pounds of open pressure at 0.550 lift. Edelbrock springs also allowed plenty of room before experiencing coil bind (up to 0.650 lift). The springs offered plenty of pressure for the mild 0.544/0.555-lift hydraulic roller cam we intended to run in our 302. The Edelbrock heads also featured a number of other nice features, including CNC port-matched intake and exhaust ports, heli-coiled rocker and exhaust bolt holes, and a 51/48-inch-thick deck surface. The heads also came assembled with springs, retainers, and guideplates. It should be noted that the head bolt holes in the Edelbrock Performer heads came drilled to accept 1/2-inch head bolts/studs. Bolt bushing kits are available from both Edelbrock and ARP to allow use of the Performer heads with the smaller 7/16-inch head bolts/studs used on the 302 Windsors.
After receiving the Performer heads from Edelbrock, we ventured out to Mira Loma, California, to visit our good friends at Westech Performance. They allowed use of their flow bench to compare the Edelbrock Performer heads to a set of stock E7TE (late-model) 5.0L heads. The stock heads were first on the bench, and the small intake (127 cc) and exhaust (44 cc) ports showed why they can be so restrictive to power. Combined with the 1.78/1.46 valve combination, the small ports flowed only 165 cfm and 113 cfm. It is interesting to note that the peak intake flow number was achieved at just 0.450 lift, a sure indication the port was too small for performance use. Obviously, the stock port was not the ideal choice for our 0.544/0.555 lift cam. The exhaust port peaked at 113 cfm at 0.550 lift, but gained only 5 cfm from 0.350 lift to 0.550 lift. This stagnation is an indication the port was also too small. That we were able to make the power we did with the stock heads is pretty amazing. Credit the use of a dual-pattern cam for offsetting some of the deficiencies in the exhaust port of the stock 5.0L head.
Next up was an Edelbrock Performer head. Both heads were flowed using the same bore plate, entry plate, and exit tube on the exhaust. Not surprisingly, the Edelbrock heads featured significantly larger ports. The intake ports measured 181 cc, while the exhaust ports measured 67 cc. These represented gains of 54 cc and 23 cc, respectively, over the stock 5.0L head. The ports were not the only advantage the Edelbrock heads had over the stockers. Even though we selected the smaller intake valves for our Performer heads, the 1.90/.160 valve combo was a sizable increase over the 1.78/1.46 valves in the stock heads. The combination of bigger valves and larger ports really made itself known on the flow bench, as the Performer head out-flowed the stock head by as much as 90 cfm on the intake and 69 cfm on the exhaust. Even at the more important 0.500-lift range (remember our 0.544/0.555 lift cam), the Edelbrock head was up by 73 cfm on the intake and 58 cfm on the exhaust. Every bit as important was the fact that the Edelbrock heads only lost out to the stock heads at 0.050 intake lift. Everywhere else, the Edelbrocks outflowed the stock heads. This was somewhat surprising considering the big change in port volumes.
After running the heads on the flow bench, we decided to see how the additional airflow translated to horsepower. To that end, we built a suitable test motor to properly compare the two cylinder heads. The 302 consisted of a 5.0L Street Fighter short block built by Coast High Performance. The stock two-bolt 5.0L block was equipped with a stock 5.0L crank (3-inch stroke), a set of I-beam rods, and forged Probe Racing pistons. The pistons were equipped with generous valve notches for piston-to-valve clearance. The flat-top design combined with the valve notches produced a static com-pression of 9.1:1 with the 61.5cc chambers on the stock 5.0L heads. The 59cc chambers on the Edelbrock heads increased the com-pression to nearly 9.4:1. The short-block was equipped with an Xtreme Energy XE266HR hydraulic roller cam that featured 0.544/0.555 lift split, a 212/218 duration split, and a 112-degree lobe separation angle. The 0.544/0.555-lift cam required a spring change on the stock heads, as the stock 5.0L valvesprings would not accept this much lift before experiencing coil bind.
After completing the short-block, the 302 was treated to the E7TE 5.0L Ford heads and an Edelbrock Performer RPM Air Gap intake. The intake was chosen to provide a broad powerband with plenty of horsepower potential up to 6,000 rpm. The dual-plane Performer RPM Air Gap manifold is an ideal choice for a street/strip performance build. The Performer RPM was topped off with a Barry Grant 650 Speed Demon carburetor. We wanted to make sure that no other component would be limiting the power potential of our cylinder heads. The final touches to the 302 included an MSD distributor set to provide 34 degrees of total timing, a set of Hooker Super Comp 151/48-inch headers, and a Borla Cat-Back Mustang exhaust. In addition to the XE266HR cam, Comp Cams supplied a set of 1.6 ratio Pro Magnum roller rockers, a double roller timing chain, and the necessary 6.250-inch pushrods for our test motor.
After installing the 302 on the dyno, we fired it up, set the timing, and allowed it a full break-in before subjecting it to any hard pulls. After the break-in, the motor was run at wide-open throttle from 2,500 rpm to 6,000 rpm. We chose a low starting point to see if the larger Edelbrock heads would lose any low-speed power compared to the stockers. With jetting on the Barry Grant carb completed, the stock-headed 302 pumped out 306 hp at 5,300 rpm and 342 lb-ft of torque at 4,000 rpm. The stock heads allowed the 302 to exceed 1 hp per cubic inch, an impressive feat in anyone's book, especially given the tiny valves and ports. Even more impressive than the peak power was the average torque production. The 302 pumped out not only 342 lb-ft, but bested 300 lb-ft from 2,500 rpm to 5,300 rpm. Given the broad torque curve, this combination would make a great street motor. Credit the small ports in the stock heads, the dual-plane intake, and the mild XE266HR cam for the shape of the curve.
After a few back-up runs, we cooled the motor and replaced the stock heads with the Edelbrock Performers. From a weight-savings standpoint alone, the Edelbrocks get the nod over their heavy iron counterparts. After installing the Performers and allowing the 302 to warm up, we were quite surprised at the results of the first dyno pull. Apparently the stock heads were quite restrictive to the 302, as the Performers upped the power peak from 305 hp to 383 hp. That's right, the Edelbrock Performer heads were worth a whopping 78 hp right out of the box. The peak torque improved as well, from 342 lb-ft to 364 lb-ft. The Edelbrock heads shifted the power curve slightly, with the peak horsepower number occurring 700 rpm later (5,300 rpm vs. 6,000 rpm). The peak torque shifted as well, but only by 300 rpm (from 4,000 rpm to 4,300 rpm). The greatest power gain occurred at 6,000 rpm, where the Edelbrock Performer heads out-powered the stock 5.0L Ford heads by a massive 92 horsepower. Performers indeed!
|Airflow Data: Stock 5.0l Head Vs. Edelbrock Performer|
|Air Flow Data At 28 In (Intake)||Air Flow Data At 28 In (Exhaust)|
|Lift||1. StockE7TE||3. Edelbrock Performer||1. StockE7TE||2. EdelbrockPerformer|
The larger ports and valves really made themselves known on the airflow bench. With the exception of a slight loss at .050 lift on the intake port, the Edelbrock Performer head easily out-flowed the smaller stock Ford head. The (intake) airflow difference was a solid 90 cfm at 0.600 lift and 73 cfm at a more important (for our test motor) 0.500 lift. From .150 to 0.600 lift, the Edelbrock head offered significantly more airflow, something that translated directly into additional power. The exhaust flow numbers were equally as impressive, with the larger Edelbrock exhaust port jumping the airflow gun on the stock port right away. From 0.050 lift all the way to 0.600 lift, the Edelbrock head was superior in terms of exhaust airflow. At 0.500 lift, the difference was over 58 cfm. This airflow difference grew to 69 cfm at 0.600 lift.