Ford Mustang Edelbrock Cylinder Heads Install and Test - Serious Performers

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!

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.