How much is a good set of cylinder heads worth on small-block Ford?

Words and Photos By Richard Holdener

One of the most common questions asked by enthusiasts is, “How much are cylinder heads worth?” Truth be told, you can replace the phrase cylinder heads with nearly any other performance component, since everyone wants to know what each part is worth, so they can add up all those numbers to achieve a final power output of their dream motor. There are many problems with this method, not the least of which is something we call the Pecking Order.

You see, in addition to the engine itself being a major variable in testing (different components will produce different gains on different combinations), gains will change based on the order they are installed. By this, we mean if we install heads, cam, and an intake, the heads will show greater gains if we test them last (after the intake and cam). The same is true of the camshaft and the intake manifold, as the gains offered by each component (over the stock version) will increase with the power output of the test motor.

The focus of this test was cylinder heads, more specifically to answer the question, how much are cylinder heads worth? The problem is, technically speaking, we really only answered the more specific question, how much are cylinders heads worth on this particular stroker combination? That said, the results of the test do demonstrate the potential of the heads, particularly at this power level. On a wilder combination, they will certainly be worth more, but on your typical street/strip stroker, the results are nonetheless valid.

Having tested heads on an otherwise stock 5.0L Ford, we can say a head swap is not the first modification to be considered (pick the cam), but the gains offered by the extra head flow will be useful after you apply the proper cam and intake manifold sometime down the line. We have seen head swaps on stock motors be worth less than 10 hp, but the same head swap on a modified stroker be worth 150 hp. Most (like ours tested here) will be land somewhere between these two extremes.

To illustrate the gains offered by a cylinder head upgrade on street/strip small-block Ford, we first assembled a 331 stroker. I mean why build just a standard-displacement 302 if you can go bigger, right? Starting with a production 5.0L block, the internals were upgraded with forged components from Speedmaster and Probe Racing. The flat-top pistons were swung on 5.4-inch forged rods and a 3.25-inch forged crankshaft. Completing the rotating assembly was a set of new Federal Mogul bearings and Total Seal ring package.

To ensure plenty of power, we added a hot hydraulic roller cam profile from COMP Cams. The XE274HR offered a .555/.565 lift split, a 224/232-degree duration split, and 112-degree lsa. The 331 stroker was first topped with a set of stock E7TE iron heads fresh off a 5.0L Mustang. The stock heads received a few mods prior to running, but only to allow them to operate with the COMP cam. The stock heads were treated to a valve spring upgrade and drilled and tapped for screw-in rocker studs and guide plates. This also allowed the use of 1.6-ratio, stainless roller rockers.

Before we could run our test on the Edelbrock Performer RPM heads, we needed an induction system, exhaust, and valve covers. Feeding air and fuel to the Ford stroker was a Speedmaster dual-plane Eliminator intake fed by a Barry Grant 750 Mighty Demon carburetor. The dual-plane design ensured plenty of torque production without sacrificing top-end power, and was a perfect match for the COMP cam and Edelbrock cylinder heads.

Finishing touches on the stroker included COMP Cams valve covers, 1 ¾-inch, Hooker headers, and an MSD distributor. The 331 also featured a TCI Rattler balancer, Milodon oil pan and pick up, and Meziere electric water pump.

Run with the stock 5.0L E7TE heads, the 331 stroker produced 346 hp at 5,500 rpm and 391 lb-ft of torque at 3,700 rpm. The stock heads offered reasonable torque, exceeding 350 lb-ft from 2,500 rpm to 5,100 rpm, but the stock heads were severely limiting peak power production. We would later find out they were even limiting torque production through most of the power curve. What can you expect from cylinder heads flowing just 157 cfm that were originally designed to feed a 225-hp small-block?

Equipped with the Edelbrock aluminum heads, the power output of the 331 jumped to 431 hp and 428 lb-ft of torque. After you have the right cam and intake, cylinder heads offer big power gains.

Compared to the stock Ford castings, the Edelbrock Performer RPM heads offered more of everything, including aluminum construction, larger valves, and increased port volumes. Where the stock E7TE heads relied on a 1.78/1.46-inch valve package, the Edelbrock heads stepped these sizes up to 2.02/1.57-inch combo. Working with the increased valve sizes was a commensurate increase in port volume. The 127cc intake and 44cc exhaust ports in the stock heads were miniscule compared to the 181cc/65cc combo used on the Edelbrock heads.

331 Ford Head Test-Stock vs Edelbrock Performer RPM
We always welcome big power gains, but it is even better when the extra power at the top of the rev range comes with no loss in low-speed torque. Equipped with the stock E7TE heads, the 331 stroker produced 346 hp and 391 lb-ft of torque. After installation of the Edelbrock Performer RPM heads, the peak numbers jumped to 431 hp and 428 lb-ft of torque. The flow numbers suggested the Edelbrock heads would support more than 530 hp on a wilder application, but they performed well on our mild 331, adding 85 hp.

All of this combined to dramatically increase airflow over the stock heads, with peak flow checking in at 277 cfm vs just 157 cfm for the stock heads. After installation of the Edelbrock heads, the power output of the 331 jumped to 431 hp and 428 lb-ft of torque. The Edelbrock head swap netted a cool 85 hp on this mild 302 stroker, showing exactly where they stand in the pecking order compared to stock heads.

Sources: COMP Cams, compcams.com; Edelbrock, edelbrock.com; Holley/Hooker/NOS, holley.com; MSD, Msdignition.com; Speedmaster, Speedmaster79.com; Total Seal, totalseal.com