Looking at the numbers, the iron heads performed better than we thought they would, while the aluminum heads were very close in terms of overall power. If you look at the overall torque curve of the four aluminum heads, all four are extremely close from 3,200 through roughly 4,800 rpm, where the Edelbrock heads begin to drop off slightly. That also shows up on the horsepower curve. While the power difference appears significant on the horsepower charts, please read the Simulated Dragstrip sidebar. We tested all five heads in a digital Chevelle down a virtual quarter-mile. What you'll discover is that this power discrepancy is not nearly as critical as it appears.
What's also interesting is that the intake flow curves on the TFS and Dart heads are almost identical, which transfers over to the horsepower and torque curves. Rather than get bogged down by too much detail about the power curves, it may be more important to point out how amazingly close all four heads were in terms of average power. With an average torque difference of only 8.7 lb-ft and an average horsepower difference of even less at 8.1 hp, there's a average spread difference of 1.5 percent. That's almost imperceptible in the car.
What all this means is that you really can't make a bad choice when it comes to any of these heads. Especially when you consider that there was a slight difference in compression. Had we evened up the static compression, it would certainly have helped the Dart and TFS heads the most, especially in terms of peak numbers, but it also means that the average differential would probably be a little wider, but still around 2 percent.
Also, since the cam was intentionally conservative, it's clear from the flow-bench data that all of these heads would respond with more power with another 0.030 to 0.050 inch of additional valve lift. That could come in the way of a switch to perhaps 1.8:1 roller rockers, because it gives us the lift without having to go to a longer duration that will only kill some of that brutal low-speed torque.
What's truly impressive is that this simple, oval-port, hydraulic roller-cammed 496 is capable of cranking out almost 630 lb-ft of torque at a very streetable 4,000 rpm with oval-port heads and a dual-plane intake manifold. We plan to bolt a single-plane intake on the Dart head package, and this will certainly push our 496 into the 600-plus horsepower zone. Either way, this is a killer power package disguised in conservative attire. So build a 496, paint the heads and dual-plane intake manifold orange, tell the world it's a mild 396, and blow their doors off. You just might get away with it-until the word gets out.