1991 GMC Syclone - Ride Of The Valkyries

Sweden Native Robert "Mr. Syclone" Pothorcki Runs 8s & Takes Title Of World's Fastest AWD SY

No different than any other Syclone fanatic who saw something special in a pickup truck that easily outperformed most import sports cars of its day, Robert Pothorcki was willing to go to great lengths to own a Sy back in 1992. What separates Robert from most owners, though, is that it took a heck of a lot more than a plane ticket and a couple tanks of gas to get his truck from Florida to his home in Gothenburg, Sweden. Since this town is better known for producing Saabs and Volvos rather than American-made turbo trucks, he had the element of surprise every time he prowled the streets or headed to the track. Shock and surprise was not just reserved for the Nordic inhabitants, but was spread to the U.S. years later when he ran 8.98 at 155 mph to become the fastest all-wheel-drive Syclone in the world.

Unlike his U.S. counterparts, Robert had little experience or help to draw from locally, making his journey to the 8s all the more challenging. Quite a few phone calls were made to Precision Turbo & Engine, as well as several other manufacturers, to get the combination dialed in. But for the most part, Robert was on his own in tuning the FAST computer and putting together this record breaking truck. Through some research he discovered that a custom ground solid roller, a Bow Tie iron block and Brodix aluminum heads were needed to make his ride a serious contender.

After boring out the cylinders to 4.030, the block was stuffed with low compression JE forged pistons, Eagle forged rods, and a Scat 3.75-inch stroke, forged, even-fire crank allowing 287 cubic inches (roughly 4.7L). Robert hogged out the heads as much as possible-increasing flow to and from the 2.08 intake and 1.60 exhaust valves, and establishing an 8.5 to 1 compression. Comp Cams chrome-moly pushrods and 1.6 ratio rockers keep the valvetrain in check. An Edelbrock carb-style single plane intake was ported to match the heads, and paired with a custom fabricated doghouse from Precision Turbo & Engine and an Accufab 75mm throttle body. Robert plumbed the intake to fit a set of PTE 96 lb/hr injectors, which are fed by a Weldon Racing 2025 fuel pump.

The airy side of the mixture is provided by a specially designed PTE GT45 ball bearing turbo (spooling around 28 psi), cooled by a custom PTE air-to-air intercooler. When Robert gets a chance to retune the FAST computer, he will also be running a 70 horsepower shot of nitrous (from an NOS kit) to further aid cooling. A Crane HI-6 Digital Ignition box, high output coil, and MSD billet distributor do the igniting. Unneeded air and exhaust is routed through an HKS GTI 60mm wastegate, custom stainless steel turbo headers, and a full 4-inch stainless exhaust. Believe it or not, this truck is street driven and meets Sweden's strict emissions laws (provided that Robert has the cat on during testing), so there are no dumps-a Borla muffler resides aft of the 4-inch downpipe and mid-pipe.

A heavy-duty 4L80E electronic overdrive tranny maintains total streetability with nearly limitless potential for torque. Robert built the tranny himself as well as fabricating all of the necessary adaptation-he was one of the first to transplant a 4L80E into a SyTy. A similar endeavor was undertaken with the rear end, as a Moser 12-bolt was retrofitted to the Sy's chassis packed with 35-spline axles, 3.42 gear and a posi. A Dynotech Engineering HD front prop shaft and custom carbon-fiber 3.5-inch rear driveshaft should be capable of containing over 1,000 horsepower and high rpm blasts down the 1320. The suspension setup is a bit non-conventional by SyTy standards in using AFCO double adjustable coilovers front and rear. The coilover suspension in the rear negates the factory leaf spring setup and uses ladder bars to compensate. In combination with the English-made 16-inch Team Dynamics Pro Race and 15-inch Mickey Thompson lightweight racing wheels, as well as the Wilwood brakes and Momo racing seat, there should be significant weight reduction despite a Swedish-spec chrome-moly roll cage. Unfortunately, Robert has not been able to weigh the truck to confirm this. But one thing is for sure: this setup definitely hooks. With Mickey Thompson 26x10.5 ET Drag slicks at all four corners, the Swedish Sy cuts a 1.38 sixty foot.

Nitrous, good track prep, and favorable DA could all put a serious dent in short times as well as ET-something Robert hoped to achieve when visiting the States last year for the SyTy Nationals. It just wasn't in the cards, though, and a few tuning issues kept him from setting any new records. But this didn't take anything away from the enormous pride Robert takes in his truck, and in himself for building it. Who can blame him?

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Check out Robert Pothorcki 1991 GMC Syclone with JE forded pistons and a PTE GT 45 Turbo featured in the 2007 April Issue of GM...
Apr 1, 2007

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