426 Crate Hemi Dyno Test

The Hemi cranked to life with the sound to match its serious performance looks. The stout street roller had the unmistakable burble of a heavy-hitting performance combo, but it wasn't so outrageous that we were afraid to run it on the street. Again, working the tuning loops, we zeroed in on the optimal jetting, and using the same 33-degree timing setting as in our previous test, we found 534 hp at 6,400 rpm. The cam change was worth 40 hp--a solid gain--and came with a good 700-rpm increase in usable powerband without detracting from power production lower in the rev range. Still, we felt the camshaft/cylinder-head combination should make some explosive power even higher in the rpm band. The key, we believed, would be to complement the combination with a change in the induction system to let it breathe even higher up the range.

With our new combo, the dual-plane factory intake manifold appeared out of place. We wanted a serious single-plane intake manifold that would add to the high-rpm breathing capacity of the Hemi heads worked by the Crane roller cam. To fill that bill, we scored a high-rise Barton single four-barrel manifold. The Barton piece has the unmistakable look of an intake single-mindedly designed for performance, and comes with Dominator-pattern carb-mounting provision. A Dominator or King Demon carb bolts directly in place, while a 4150 standard-pattern carb requires an adapter. We opted to move to a large-bolt-pattern carb--a 995 King Demon.

With the intake and carb change, our Hemi took on a different character, at least in the looks department. The wickedly sweeping divorced runners of the Barton intake and the fat King Demon carb had the look of serious hardware. While we found the appearance satisfying, we were more interested in the numbers. It seemed a shoe-in that the induction was the cork in our previous combo, and confidence was running high that the upgraded induction would let the rest of the combo swill some serious air and turn a number.

We found tuning the King Demon no more difficult than a conventionally sized carb, and we limited our tuning to running a standard jetting loop. The King Demon features replaceable air-bleed circuits; however, no changes were required to get a fine-looking fuel curve. With the induction change, we hit paydirt, recording 594 hp at 6,600 rpm within five dyno pulls. As is typical with a single-plane versus a dual-plane, the lower end of the torque curve softened some, but the high-end charge really woke up.

The intake and carb were worth another remarkable 60 hp, pushing the output of our 426-cube engine so close to the 600hp number we could taste it. We wanted to push the engine over the magic 600hp mark, but our dyno time was winding down. A little more flogging or a change to synthetic lube would have easily moved it over the hump.

Stashed in the corner at Westech was a set of TTI 21/4-inch big-tube Hemi headers. On a 426-cube engine, we suspected they would be a little too much, but at least we gave them a try. Time was short, so we left our oh-so-close-to-600hp previous combo and made the move to the fat-tube headers. Unfortunately, they were a little too much for our combo, and we saw power drop over most of the range, with the exception of a blip above our previous output line in the midrange. It was clear we weren't going to hit our magic number with this combo, but, sorry pal, we were way past the two-minute warning, and there was no time to go back. Too much header cost us torque, power, and time.

So, how do we sum up this little adventure? Well, we can say what Mopar fans have known for years--Hemis make power. We had close to 600 hp on hand, close enough to call it there. When you consider we got there with only 426 cubes and the stock cylinder heads, it walks the walk. Try writing a list of other production engines that will do the same, and you won't have to worry about running out of ink.