It wasn't long ago that the Mopar enthusiast running a big-block had very few choices when it came to cylinder heads. Most of us would refresh our steel heads and do a little port work ourselves or pay a professional to try to make more power. The only economical upgrade we had was to go to a 452 casting with hardened valve seats compatible with the crappy fuel we could get at the local station. Those with deep pockets could upgrade to an aftermarket cylinder head, but unless you were a serious racer the cost kept most of us out of the market. What we longed for was a quality aluminum head that made good power and would perform well in street and race applications, while not blowing our automotive budget.
Several years ago when Edelbrock produced their Performer RPM heads, we felt a great void had been filled in the Mopar aftermarket. While we have run the heads with great success on street/strip engines, we have always wondered how the Edelbrocks compare to a set of fully ported steel heads. We figured that a trip to the dyno was the only way to know for sure, so we packed up a worked iron head 440 and a set of 84cc Edelbrocks and headed over to Autoshop Racing Engines in Orlando for a little dyno thrashing.
Our test mule is a steel crank 440 that sees track duty in our friend Garret Struck's '72 Duster bracket racer. We felt this motor would be a great test of the Edelbrock heads as it is a solid combination that the average racer can build . . . not stock, but nothing exotic either, just a stout 440. The basic combination includes an older Torker intake manifold with an equally old Holley 1050 Dominator, 12.5 to 1 dome pistons, aftermarket steel rods, a .590 lift solid flat-tappet cam, and a set of fully ported and polished 452 casting steel heads. Fully ported and polished is actually an understatement as these heads have received extensive port, bowl, and seat work, as well as 2.20 intake and 1.81 exhaust valves. We figure these heads flow about as well as a set of 452 castings can, so we were a little skeptical that the out-of-the-box Edelbrocks would outperform them . . . boy, were we wrong.
Our initial dyno pull was to establish a base line for the combination. We also needed to address a detonation issue since the car seemed to run better at the track with C16 (116 octane) fuel than it did with the C12 (112 octane). Our first pull was with C12 and 42 degrees of total timing and slight spot detonation was evident. Our second pull with the C16 cleared up the problem and netted 5 additional peak horsepower, as well as 14 lb-ft of peak torque! All subsequent dyno pulls were performed using the C16 fuel. Remember that fuel requirements are based on many variables, not just the compression ratio of your engine. Our detonation issue was related more to the open combustion chamber design of the 452 casting cylinder head than the compression ratio of the engine.
With our baseline established, we felt the 1050 Holley may be a little much for our .030 over 440, so we changed carburetors to a Holley 950hp unit to check for over-carburetion. The engine fired immediately and seemed crisp with the 950, but we actually lost substantial horsepower and torque, and our air/fuel ratio went to a rich 12.2 at peak rpm, indicating that our engine was now under-carbureted. The Holley 950HP is a nice piece, just a little small for our combination. With the carburetion issue settled, we switched back to the 1050 Dominator, and it was time to swap heads.