Low-Buck 500hp Chevy Duramax - Six-Speed Sleeper

A 13-second, 500hp, Manual-Transmission Duramax Built on a Budget

Jason Sands
Oct 1, 2011
With more than 10 years of tuning and fiddling since the Duramax diesel’s 2001 inception, it’s become clear just how potent these 32-valve powerplants are. Rated at 300 flywheel horsepower from the factory, it has now become all too easy to double the power output of the 6.6L engine. One of the most coveted performance goals is to break the 500-rwhp mark with a near-stock truck. We’re here to tell you that yes, it can be done—and we recently found an awesome example of a near-stocker that rocks.
Photo 2/9   |   six Speed Sleeper chevy 2500 Front Three Quarter
The Rival Blue ’04 Chevrolet 2500 you see on these pages belongs to Dan McNulty of Westerville, Ohio. In addition to making 515 hp at the wheels, it also cracked the four-digit torque mark with 1,010 lb-ft. Upon opening the hood, the engine looks downright stock, which confuses many. Part of the magic comes through EFILive tuning courtesy of past Diesel Power Challenge competitor Jeff Dean, and a 4-inch downpipe, 5-inch exhaust, and 6-inch stack leave room for power to grow if Dan ever decides to step it up. Other than an EGR delete and AirDog 150-gph lift pump, the rest of the engine is factory fresh.
Just because the engine is mostly stock, doesn’t mean the rest of the truck is. You see, Dan is an avid drag racer and sled puller, so he built the rest of the truck to be as bulletproof as possible. The chassis has a set of custom-built stainless steel traction bars, a custom front crossmember, and only two leaves in the rear. The result is a 4-inch drop that is advantageous in both sled pulling and drag racing. The front end has been beefed up with a billet centerlink and tie-rod sleeves from Crank It Up Diesel. The hitch has also been relocated to give him a little more leverage when hooked to the sled.
Photo 3/9   |   The cool traction bars, which are made out of stainless steel, really work well with the factory Rival Blue paintjob. Four 295/70R17 Nitto Terra Grapplers on powdercoated Hummer H2 wheels provide traction at the track, on the street, and while hooked to the sled.
Perhaps the biggest surprise of the truck has to be the fact that there’s no Allison transmission! Instead, Dan shifts his own gears via a factory ZF-6 manual transmission. The clutch didn’t last much past stock power levels, so it was replaced with a monstrously tough triple-disc unit from South Bend Clutch. While the general consensus is that manual transmission trucks can’t be fast, Dan would disagree, as he runs 13.50s all day long—with a best of 13.41 at 100 mph. “You have to shift like you’re trying to break it, or you’ll miss a gear,” Dan said. He told us he’s raced similarly powered Allison-transmissioned trucks, and he is usually neck and neck with them. Having an SFI-rated clutch also makes him feel better about leaving the line at 4,600 rpm during a pull.
While Dan’s Dmax may not be a 1,000hp truck or competitive in the crazy Ohio 2.6 Class, it’s a great example of what can be done on a budget. Often, manual transmission trucks are cheaper to buy because they aren’t as desirable to the general public, but Dan told us someone could probably duplicate his Chevy (which he bought with only 49,000 miles) for about $22,500. It’s also proven to be ultra-reliable and has more than 40 hooks to the sled and 70 to 80 dragstrip passes. If that isn’t a great fun-per-dollar ratio, we don’t know what is.



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