Diesel World

DIAMOND DUSTER

VINTAGE GMC C10 BUILT FOR PRO STREET

- TEXT BY FRANK STROUD PHOTOS BY RON MCKINNIS

As race season heats up, racers and builders across the land prepare to roll their rigs into race venues all over the country. Many will campaign old vehicles that have in one way or another been reinvented for the new year: new paint schemes, new body work, new turbos, new engines, new names. Others will be rolling out something entirely new. Performanc­e Authority out of Bend, Oregon, falls into the latter category. You’re looking at their Pro Street entry for 2017, a ’60s-era GMC C10 which has essentiall­y been torn down from top to bottom and completely reassemble­d from the ground up.

The C10 was originally purchased in the spring of 2014 for the paltry sum of $1,200. Two and a half years and a good six figures’ worth of sweat, blood, grease, metal shavings, bruised knuckles and capital outlay, it was finally transforme­d into what the builders affectiona­tely call “Demon Smurf.” In addition to racing, it was also carefully put together to serve as an exhibition piece for Performanc­e Authority and Diamond Eye Performanc­e in the Diamond Eye booth at SEMA 2016. Believe it or not, it also remains street legal for what Performanc­e

Authority owner Bennett Leffler calls “Saturday night ice cream runs.”

DIVIDE AND CONQUER

Since the plan was to run in Pro Street, no time was wasted in dicing up the chassis and back-halving the truck with a 1-3/4-inch chromoly steel framework to support a four-link setup. The chassis underpinni­ngs were bent, welded and laser-cut offsite at 369 Custom Fabricatio­n, Crawl2run, and Diversifie­d Products (all three also located in Bend),

then returned to Leffler’s shop for final assembly. The rear axle is comprised of a Fab9 nine-inch chromoly housing and a medley of Strange Engineerin­g components—the same Strange Engineerin­g that supplies drive components to Top Fuel NHRA dragsters. The solid axle is suspended beneath the chassis by 200-pound coilover springs and Varishock double-adjustable dampers.

The C10’s cabin section retains most of its original outer metal but has been reinforced with a multi-point chromoly tube cage jigged, bent and welded by 369 Custom. The front suspension employs 550-pound coil springs to shoulder the heavy load set by the planned Duramax power unit. The springs are wound over Varishock double-adjustable dampers in a coilover configurat­ion similar to the rear. The front end was also improved with tubular control arms adapted from a Chevelle applicatio­n, as well as a rack-and-pinion steering assembly stolen from a Ford Thunderbir­d.

STORM SYMMETRY

With the front clip removed, the motivation and raison d’etre for all this custom structural work is

THE C10 WAS ORIGINALLY PURCHASED IN THE SPRING OF 2014 FOR THE PALTRY SUM OF $1,200.

a sight to behold, each half of the powerplant and its individual induction system a virtual mirror image of the other. The center point, ground zero so to speak, is a reinforced ’06 LBZ Duramax largely built to spec by Industrial Injection in Salt Lake City. Pistons are swung by forged Cp-carillo rods, which in turn spin a blueprinte­d Callie billet crankshaft encased within the stock iron block. Cnc-ported factory heads top the block; a Hamilton alternate-firing-order camshaft was installed to actuate the stock valves. Fuel is supplied via Dynomite Diesel 150% over injectors fed by dual Industrial Injection 85% over CP3S, which in turn are fed by dual FASS 150 lift pumps pulling fuel from a Pyrotect 15-gallon aluminum cell mounted far aft at the rear of the chassis. At the truck’s other end, another tubular chassis extension supports a substantia­l aluminum radiator core and Permacool electric fan assembly.

The hard-drinking fuel delivery system merges diesel fuel with an angry whirlwind of supercompr­essed air courtesy of modified twin Borg Warner S369SX-E turbocharg­ers— 69mm compressor, 88mm turbine, 0.91 AR housing—each mounted on its own custom stainless steel header fabricated by Metal Art, and each pushing between 40 and 45 psi when tuning is finalized. After driving the twin compressor­s, exhaust exits through a dual straight-pipe system fashioned by Diamond Eye Performanc­e. Each side dumps through oval tips that emerge from underneath the chassis just in front of the rear slicks. A Suncoast 48RE competitio­n gearbox with standalone PCS controller transfers shock and awe via a custom-built driveline with 1410 Series U-joints to a 3.50 Strange spool turning 40-spline axles. Finally, the rubber

meets the road via 33x17.5-inch Hoosier drag slicks wrapped around 16x16-inch Race Star monocoque wheels.

Chassis wiring was provided by Ron Francis and engine wiring was performed at PA. Preliminar­y air/fuel tuning was performed by “Idaho Rob” Coddens of ATP Truck, Meridian, Idaho, via EFI Live. Initial testing will have already begun by the time you read this; for now, engine output is estimated based on similar builds. Leffler estimates horsepower to be in the range of 1,500 on fuel alone, and a conservati­ve 2,000-plus when the Nitrous Express two-stage progressiv­e system is toggled on. Once final tuning and chassis setup is complete, Leffler is eyeballing 8s in the quarter mile.

BUSINESS SUIT

In spite of its purported street-legal status, the Demon Smurf’s cabin is necessaril­y lean on creature comforts. Occupants strap into Corbeau race buckets and are snugly secured by Pyrotect harnesses. Driver input is facilitate­d by a Forever Sharp steering wheel, which directs the 17-inch Race Star Recluse front wheels via that Thunderbir­d rack. Gear selection is actuated by a B&M linkage and sequential shift lever. The whole of instrument­ation is contained in an Autometer LCD data acquisitio­n module set into the dash; the unit is fully customizab­le by the driver to display virtually any aspect of the engine’s operation and performanc­e. Obviously, with the back-end race reconfigur­ation there’s very little left in the way of traditiona­l pickup bed. The area is filled primarily with substantia­l carbon-fiber wheel arches and an extension of the roll cage that ties into the chassis and holds the twin 15lb Nitrous Express bottles. Last but certainly not least, braking is accomplish­ed by hard-biting Wilwood hardware at all four corners.

The previously mentioned front clip, formed by US Fiberglass in the image of a 1965 GMC, was prepped and painted (as was the rest of the exterior and interior) by Greg’s Custom Creations, also located in Bend. The powdery blue is a custom Sikkens hue mixed to mimic a period GM color and evoke nostalgia for the good old days when men were men and trucks were trucks; likewise, the white is modeled after Ford’s Oxford shade from the 1980s.

THE BUILDERS AFFECTIONA­TELY CALL IT DEMON SMURF.

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 ??  ??  Massive Hoosier drag slicks help put the power to the pavement. Note the custom Diamond Eye exhaust exiting just in front of the rear tires.
 Massive Hoosier drag slicks help put the power to the pavement. Note the custom Diamond Eye exhaust exiting just in front of the rear tires.
 ??  ??  Dual 15lb Nitrous Express bottles and the dual FASS lift pumps reside in the bed between the cab and the rear-mount Pyrotect fuel cell.
 Dual 15lb Nitrous Express bottles and the dual FASS lift pumps reside in the bed between the cab and the rear-mount Pyrotect fuel cell.
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 ??  ??  With the one-piece fiberglass front clip out of the way the 1,500hp (est.) Duramax powerplant is clearly visible.
 With the one-piece fiberglass front clip out of the way the 1,500hp (est.) Duramax powerplant is clearly visible.
 ??  ??   The interior is all business—everything you need, nothing you don’t.
  The interior is all business—everything you need, nothing you don’t.
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