It's no secret that it takes a well thought out combination to win the AMSOIL/Mopar Muscle Engine Challenge, especially since each year we change the rules a bit, featuring a different popular Mopar powerplant. Each year our dyno competition is held at Comp Cams' Memphis, Tennessee, facility, and this year's contest featured the Chrysler small-block, featuring the new "X" casting cast-iron cylinder heads from Racing Head Service (RHS). We allowed the engines to rev high this year, eliminating the upper rpm limit, and all of the engines were judged by the same basic standard, horsepower per cubic inch.
For the second year in a row, Schurbon Engine and Machine won our annual contest, this year with a somewhat unconventional 340 cubic inch de-stroked small-block Mopar. Engine builder Scott Schurbon used some sharp rules interpretation this year, finding advantages that allowed his team to win the close contest. Each year our competitors find areas in the rules where they can gain an advantage, and this year Scott Schurbon will be the cause of more than one rule revision for next year's contest. We congratulate Scott for his win, making a dominant 1.504 hp per cubic inch, and we look forward to seeing him in next year's contest.
Promax Performance brought a bullet this year, earning second place in the dyno contest by making impressive power with their .030 over 340. Engine builder Ben Gorman has always brought strong reliable engines to our competition, but this year they pushed the limit with a big Comp solid roller camshaft and nearly 12.5:1 compression. The Promax entry performed well on Comp's dyno, making over 500 hp for a 1.452hp per-cubic-inch factor, nearly as much as the first place entry of Schurbon. This month we'll go inside both these powerful small-blocks, showing you what's inside the top two finishers in the 2010 AMSOIL/Mopar Muscle Engine Challenge.
As the returning champion,...
As the returning champion, and drawing the first dyno session of the contest, the pressure was on Schurbon Engine and Machine. Adding to the drama was Scott Schurbon's decision to attempt a cam swap during the timed period of the contest before the judged pulls.
Schurbon Engine And Machine
We enjoy all of the competitors who've entered our annual dyno contest and have learned from all of them, but one engine builder who pushes rules scrutiny to the limits is Scott Schurbon of Schurbon Engine and Machine in Maquoketa, Iowa. This year Scott read the rules carefully, deciding that with the cast-iron RHS cylinder head and horsepower per cubic inch determining the winner, that a 340 cubic inch displacement engine would be the best choice. Additionally, in order to fit larger valves in the heads without cylinder wall interference or valve shrouding, he de-stroked the small-block to 3.250 inches and over-bored the cylinders to 4.080 inches. The result was a small-displacement engine with enough bore size to really let the RHS cylinder heads flow properly, as demonstrated by the nearly 525 hp this 340 made during a qualifying pull.
Once your eyes adjust to the...
Once your eyes adjust to the bright color, check out the water pump. The rules said engine driven water pump, but Scott contended it didn't say the pump had to be driven by the engine. (Editor's note-we fixed that glitch, Scott.) And the fuel pump? If you look closely you'll see it's routed to the crankcase, drawing a vacuum and allowing lighter tension rings.
As the first contestant Monday morning, all eyes were watching Schurbon Engine and Machine as the team bolted their engine on Comp's dyno. Causing controversy right off the bat, Scott Schurbon mounted an electric motor to drive his water pump, though the rules read "crankshaft driven water pump." Scott's claim that his was a "crankshaft-driven" water pump held up since technically it meets the criteria of the way the rule was written, and since the rules didn't say it has to be driven by the engine (look for a revision next year). Next, Scott and his team began bolting on an engine-driven mechanical fuel pump, initiating a barrage of "you know the dyno has a fuel pump" comments. As the team continued it became apparent that this was going to be used as a vacuum pump, drawing negative pressure on the crankcase to help seal lighter tension piston rings.