Thanks. We spend all year mocking the arcane, imprecise, Iron Age technology of the pushrod, and every year you, our faithful but apparently inattentive reader, vote some pushrod monster into the Ultimate Street Car Challenge. Last year it was Geoff Bennett's supercharged 4.9-liter 5.0 Mustang, a car that took the bizarre honor of being the most powerful single-engine car on the dyno. But the Mustang only had 16 pushrods, and being a dedicated drag racer, it was never a threat for overall victory.
But you had to vote this thing in. Twenty pushrods in all, 10 of them opening massive 2-inch intake valves, feeding an engine more than twice the size of the next biggest powerplant in the group. Not only does this beast pack the displacement for which we've been told there's no replacement, it packs steamroller Hoosier rubber and a suspension and chassis tuned for the track. This thing is a ringer for the dynosaur team.
This particular Viper started life as an ACR model, which is factory rated at 460 hp, 10 ponies more than a Viper GTS. But when Paul Mumford of Yorba Linda, Calif., first brought it to the dyno, he found it to be 25 hp weaker than his previous plain, old pedestrian street Viper. That pissed him off. His solution? Send the whole car to EMI Racing.
There, Eric Messley oversaw a transformation that should give every other USCC competitor cold sweats. First the engine came out and went to Caldwell Development (CDI). John Caldwell's engine-building resume stretches from building the giant-killing BRE Datsun engines 30 years ago, to crafting the thundering Viper V10s that took Le Mans in 1998 and 1999.
Anticipating the sustained high revs (that's a relative term in the Viper world) of the track, Caldwell ripped out the whole reciprocating assembly, dropping in a stronger forged crank and rods, and adding forged pistons with a modest 10:1 compression ratio. Displacement remained the same.
A new camshaft-that's singular, as in one camshaft for the intake and exhaust valves-was ground to Caldwell's specs to give seriously high rpm breathing ability without losing that legendary Viper torque. It opens staggeringly large valves through 20 pushrods and 20 1.7:1 roller rockers.
The heads were ported by CDI, and the intake manifold was Extrude Honed. Gorgeous CDI headers, like stainless-steel snake pits, adorn either side of the engine, feeding exhausts by Bondio Fabrication that knock a few decibels off before belching the hot, spent gases onto the ankles of unsuspecting pedestrians. You've gotta love side pipes. With all the breathing work done, the stock ECU was re-tuned by the Viper shop to make it all work.
So far this is just another pushrod story of gratuitous horsepower and abundant displacement. Now it gets good. EMI Racing tore out ACR's Koni race shocks, and replaced them with triple-adjustable Penskes. EMI also installed 600 lb/in. springs up front and 850s in the rear. The motion ratio of the Viper's double-wishbone suspension makes these spring rates far more reasonable than they may first appear.
Then all the stock rubber was replaced with mono-balls at the end of all the A-arms. For tires, Mumford runs 305/30ZR-18 Hoosiers on the front. On the front! And 335/35ZR-17s go in the back. Ponder that for a second. If you lined up all that rubber side by side, you'd have more than four feet of Indiana gummy. That's just silly.
Brakes, a notorious Viper weak point, are addressed with 14-inch Stoptechs in front and 13-inch Stoptechs out back. Repeat. Thirteen-inch Stoptech brakes in the back. There is a lot of car to stop.
OK, so this is a fast Viper. It has stupid horsepower, huge brakes, and an embarrassment of rubber. It still takes a very talented driver to milk the potential from any Viper, and Paul Mumford packs credentials. Mumford is a regular at Viper track days, Porsche Owners Club track days, Touring Car Club track days... Pretty much if there's a track and a day, Mumford and his Viper will be there.
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