DIAMOND DUO | A Pro Street ’60s-era GMC and its hauler

A Set of Track-Ready Trucks

DEMON SMURF ONE SLICK VINTAGE GMC RACER

In the racing community, many campaign old vehicles that have in one way or another been reinvented: new paint schemes, bodywork, turbos, engines, names. Others roll out something entirely new and exciting. Performance Authority (PA) out of Bend, Oregon, falls into the latter category. What you’re looking at is their Pro Street entry, a ’60s-era GMC that has essentially been torn down from top to bottom and completely reassembled from the ground up.

The GMC was originally purchased in the spring of 2014 for the paltry sum of $1,200. After a few years and a good six figures’ worth of sweat, blood, grease, metal shavings, bruised knuckles and capital outlay, it was 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 the two companies at SEMA (Diamond Eye Performance and Performance Authority), and believe it or not, it also remains street legal for what PA 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 1 ¾-inch chrome-moly steel framework to support a 4-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 9-inch chrome-moly 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 coil-over springs and Varishock double-adjustable dampers.

The GMC’s cabin section retains most of its original outer metal but has been reinforced with a multi-point chrome-moly 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 coil-over 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 of this custom structural work is a sight to behold, each half of the power plant and individual induction system is a virtual mirror image of the other. The center point, ground zero, so to speak, is a reinforced 2006 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 Callies billet crankshaft encased within the stock iron block. CNC-ported factory heads top the block and house a Hamilton alternate-firing-order camshaft 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 extension supports a substantial aluminum radiator core and Perma-Cool electric fan assembly.

The hard-drinking delivery system merges fuel with an angry whirlwind of super compressed air courtesy of modified twin Borg Warner S369SX-E turbochargers—69mm compressor, 88mm turbine, 0.91 AR housings—each mounted on its own custom stainless steel header fabricated by Metal Art and each pushing between 40-45 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 via angle-cut tips that emerge from underneath the chassis just in front of the rear racing 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 33×17.5-inch Hoosier drag slicks wrapped around 16×16-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. The engine output is estimated based on similar builds; Leffler reckons 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.

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 Auto Meter 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.

“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 …”

Obviously, with the back-end race reconfiguration there’s very little left in the way of a traditional pickup bed. The area is filled primarily with substantial carbon-fiber wheel arches and an extension of the cabin roll cage that holds the twin 15-pound 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 ’80s.

[divider] TRUCK SPECS [/divider]

OWNER

Performance Authority   
1965 GMC
Bend, OR

ENGINE

• 6.6L LBZ
• Callies crankshaft
• CP-Carillo rods
• CNC-ported heads
• Alt-fire camshaft
• Dual FASS lift pumps
• Dual Industrial Injection 85% over CP3s
• Dynomite Diesel 150% over injectors
• Twin Borg Warner S369SX-E turbos
• Industrial Injection plumbing
• Custom 321 exhaust manifolds by Metal Art
• Diamond Eye Performance dual straight pipes
• Twin 15-pound Nitrous Express bottles
• Suncoast 48RE transmission with PCS standalone controller
• Custom driveshaft
• Fab9 rearend
• Strange Engineering spool
• 40-spline axles

 CHASSIS & SUSPENSION

• Chrome-moly steel frame and cage
• Chevelle tubular control arms
• Ford Thunderbird steering
• Rear 4-link
• Varishock double-adjustable coil-overs
• Wilwood Dynalite front brake assemblies and Dynapro rears

WHEELS & TIRES

• 17×4.5 and 16×16 Race Star
• 27×5 Hoosier fronts and 33×17.5 Hoosier slicks rear

BODY & PAINT

• US Fiberglass front clip
• Powder Blue and Oxford White paint mixed with Sikkens material

INTERIOR & STEREO

• Corbeau race buckets
• Pyrotect harnesses
• Auto Meter LCD data acquisition module
• Custom sheet metal work

 THE SPIRIT OF ‘ 48

A Purpose-Built 1948 Ford COE Hauler

The other half of this dynamic duo is Diamond Eye’s very unique and supremely badass ’48 Ford COE hauler. With the GMC riding piggyback, this vehicle was the company’s centerpiece at its SEMA booth and now serves as its promotional flagship. With the GMC hoisted up onto its bed, the pair cannot help but make the grandest of entrances. The Ford C series had a cab-forward design that looked like nothing so much as a Viking helmet on wheels. Today, these trucks are highly prized, and with this build Diamond Eye wanted to take advantage of that. So, as with the GMC, it was built to be a fully functional yet easy-on-the-eyes showpiece that in the process became what is possibly the meanest tow rig on the road.

The cab section on this one might be vintage Ford, but underneath the foundation for this project is in fact a GM C-30 chassis, so it does share some mechanical DNA with the GMC racer. The frame is fully boxed for bullet-stopping rigidity and has been extended a healthy amount. The rear axle was also relocated further back; it is a 14-bolt GM unit retrofitted with a Nitro gear set and differential cover. The suspension is bolstered by specially fabricated arms and leveled with Firestone Ride Rite airbags. Rancho 9000 XL dampers smooth out the ride. A similar setup resides in front. The COE’s preferred stance is dumped to the ground over 22-inch American Force Avid wheels. The hauler bed is a fully custom unit blueprinted and built by Anvil Fabworx (also in Bend). It incorporates yards of glossy black custom sheet metal (paint and Diamond Eye graphics by Greg’s Custom), integrated dry boxes and storage cubbies, and some innovative engineering features that play into the truck’s functionality.

Tucked Into Bed

Production-line diesel COEs ran period power plants from Caterpillar, Cummins, Detroit, and yes, Ford. This one runs a much more modern built 1998 12V Cummins assembled by Bennett Leffler. Furthering its full-custom nature, the Diamond Eye COE is no longer technically a cab-over design; the engine is in fact mounted amidships, behind the cab and installed below bed level using custom mounts fashioned by PA. The cylinders in the straight-six block have been bored out 0.020 inch and loaded with coated Mahle pistons. ARP bolts fasten a stock, albeit ported, cylinder head to the block. An Industrial Injection induction intake horn gets a healthy supply of air from the compound BD Diesel Super B Tow turbos singing to the tune of 55 psi. Compressed air is cooled by a side-mount custom-made intercooler before making its way into the Cummins. Fuel is drawn by a FASS 150 lift pump from a custom cell mounted, like the engine, below the bed. Juice is directed through a Dynomite P-pump and atomized by Dynomite Stage 2 injectors. Exhaust gas is directed from the BD turbos by a Diamond Eye-fabricated dual-pipe system that exits on either side of the truck through ports cut into the bed’s side panels just in front of the rear wheels. As to its high functionality, the bed’s front corners feature large cutout sections with mesh overlays that allow air to flow directly into either side of the engine compartment, passing over the intercooler core on the driver’s side and across the PermaCool transmission cooler on the passenger’s side. The transmission itself is a 2006 Allison 1000 mated to the Cummins 12V via a Cummins Allison conversion kit. The six-speed gearbox has been given an ATS Stage 6 overhaul.

Like the GMC, chassis wiring on the hauler was also masterminded by Ron Francis, providing illumination to the Vision X Black Vortex LED headlamps and Volkswagen LED tails. Vision X red LED mood lighting also provides illumination up and down the hauler bed. In case you don’t see it coming, the COE signals its arrival with Kleinn Demon Model 730 air horns you might find on a Union Pacific diesel locomotive. The horns and the air suspension are fed by an AccuAir air system also incorporated into the hauler bed. The bed’s high end is fitted with a Warn Zeon Platinum 10-S winch to hoist and secure its payload.

“The two trucks did make their debut together and may be seen yet again together outside the pages of this magazine …”

Unlike the GMC, the COE’s interior remains comfortable enough for extended road use. The original 1948 trappings have been replaced with a pair of Ram bucket seats from this century. They were skinned by Roadwire in black leather with red quilted stitching. Roadwire also applied black ultrasuede for the cab’s ceiling and back wall. A Flaming River steering wheel sends directions to the front wheels via Flaming River steering column. Dakota Digital instrumentation provides visual feedback to the driver.

The two trucks did make their debut together and may be seen yet again together outside the pages of this magazine, but due to logistics and the COE’s slammed-to-the-weeds profile, it is not the GMC’s sole method of transport to events. The Diamond Eye crew doesn’t completely rule out the possibility of a reunion, if for no other reason than to show off. 

[divider] TRUCK SPECS [/divider]

OWNER

Diamond Eye Performance   
1948 Ford C Series
Athena, OR

ENGINE

• 5.9L 12V Cummins
• Mahle pistons
• Ported stock heads
• FASS 150 lift pump
• Dynomite Diesel P-Pump
• Stage 2 injectors
• BD Diesel Performance Super B twins
• Radiator Supply House intercooler
• Diamond Eye Performance dual exhaust
• Allison 1000 with ATS Stage 6 rebuild
• PermaCool transmission cooler
• GM14-bolt rearend
• Nitro gear set

 CHASSIS & SUSPENSION

• GM C-30 chassis
• Firestone Ride Rite airbags
• Rancho 9000 XL shocks
• Choppin’ Block Chassis Products control arms
• Kleinn Demon Model 730 air horns
• AccuAir air system
• Warn Zeon Platinum 10-S winch

 WHEELS & TIRES

• 22×8.5 American Force Avid
• 265/45R22 Toyo Proxes II

BODY & PAINT

• Full custom bed with integrated dry boxes and storage cubbies
• Vision X Black Vortex LED headlamps
• Volkswagen LED tails

INTERIOR & STEREO

• Dodge Ram seats
• Roadwire leather upholstery
• Flaming River steering column
• Dakota Digital gauges