The 2008 Amsoil/Mopar Muscle Engine Challenge - Promax Carbs & Performance Parts

To see video of Promax's dyno run click here.

The Amsoil/Mopar Muscle Engine Challenge is one of the most well-received technical subjects we cover here at Mopar Muscle magazine, and we've always had an eager list of participants willing to build engines for our competition. This year, however, for reasons beyond their control, both Diamondback Engines and Mid America Racing Engine had to drop out of the contest, leaving us with two vacant spots to fill. With the deadline of dropping the engines off at the Mopar Nationals looming near, we offered the two vacant positions to this year's alternate applicants, and engine builder Ben Gorman of Indianapolis, Indiana-based Promax decided to take us up on the offer.

Knowing time was short, Ben was pretty sure he and his crew couldn't build an engine from scratch for the competition. So with only a few weeks to work with, Ben decided to simply freshen up the 440 his shop regularly uses to dyno the Six-Pack induction systems Promax is known for. Since our contest this year required all competitors to utilize the same Indy SR cylinder heads, Ben took advantage of having a customer's set of heads already in his shop and suggested that he port the heads for free in return for being allowed to run the heads on the Engine Challenge entry. The customer thought this was a great idea and quickly agreed to let Promax use the heads for the competition.

With a plan in place, Ben and the team from Promax got to work assembling their entry. Knowing he simply didn't have time to change pistons for increased compression, or to lighten the rotating assembly, or to perform all the other time consuming tasks it takes to win a dyno challenge, Ben and the Promax crew decided it didn't make sense to go for the win in this year's contest, but rather build a solid engine that would showcase their trio of specially built Holley carburetors. Because the relatively low compression of this engine combined with the limited peak power achievable with a Six-Pack intake would limit horsepower, Promax simply put together a moderate street engine with great torque and power curves, impressing us with their numbers given their time constraints and combination.

On the dyno, it was apparent that the Promax 440 was a reliable, relatively mild street engine. This engine idled nicely, had plenty of manifold vacuum, and ran great on Rockett Brand 93 octane pump gasoline. Heck, at only ten to one compression this engine would have likely run fine on fuel with even less octane. During their dyno session, the crew from Promax optimized their combination through jetting and ignition timing changes, tuning the engine to more power and torque on each pull. Achieving a best pull of 554.1 hp and 526.3 lb/ft of torque for a combined score of 1070.4, engine builder Ben Gorman and the guys from Promax were happy to have competed in this year's challenge, earning a seventh-place finish. This month we'll go inside their powerful big-block and show you just how they did it.

While engine builder Ben Gorman may have preferred to start from scratch to develop a short-block for this year's challenge, as an alternate entry he just didn't have that luxury. Knowing that his shop's regularly dyno'd 440 test mule met the rules of our competition, Ben used the existing short-block as a basis for his entry. As a .030 inch over factory 440 with a stock forged crankshaft, ARP bolts, stock rods, and Diamond flat-top pistons, this engine is typical of the engines many of our readers build. Far from exotic, this 440 is just a solid big-block with pump-gas-friendly ten-to-one compression. Of course Ben freshened the bottom end with new bearings and inspected the short-block prior to bolting the factory oil pan back in place and deeming the short-block ready for competition.

To top their 440 short-block, Promax was required to use the same Indy SR cylinder heads as the rest of the competitors. Rather than porting their heads to Max-Wedge port dimensions for maximum flow, Promax opted to keep the same port dimensions as factory 906 heads because too much port volume wouldn't match the rest of their combination. Of course the heads were treated to bowl blending, and ported to the extent possible while retaining the factory port openings, then treated to a multi-angle valve job, stainless steel valves, and new Comp Cams roller valvesprings. Harland Sharp roller rocker arms were employed to actuate the valves. For induction, Promax again would like to thank a generous customer who allowed them to use a Weiand high-flowing Six-Pack intake manifold. While most Six-Pack intake manifolds are limited by their dual-plane design, the Weiand unit has a raised open plenum, making it a better choice for peak power. To mix the air and fuel, a trio of Promax prepped Holley two-barrels were utilized. Having special metering plates allowing jet changes in the outboard carburetors, the Promax Six-Pack carbs pretty much set the standard for three deuce tuning.