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Mechanicalocity: Peterbilt Street Rod

V-12 Detroit Diesel-Powered Hot Rod to Fuel Your Dreams

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If you're much of a gearhead, you've probably heard the name Randy Grubb. Randy is half of the "Blastolene Brothers," a demented duo of metal artists and custom coachbuilders who love to do things differently, and by "differently" we mean "gigantically." Randy and his fellow craftsman and hot-rod zealot Michael Leeds have teamed up for a handful of high-profile and large-scale projects, including the Blastolene Special and Big Bertha, both gloriously oversized roadsters with monstrous V-12 engines pulled from a Seagrave fire truck and a Patton tank, respectively. While each vehicle was built in separate states-Randy's in Grant's Pass, Oregon, and Michael's in Santa Cruz, California-the two builders shared their talents and techniques to create vehicles that wouldn't have been possible otherwise.

With Randy's V-12 affliction and his propensity for building overscaled customs, it's no wonder he ended up choosing a Peterbilt. Of course, looking at the finished product it makes perfect sense, but it takes someone with the right eye to spot the potential in a gargantuan truck cab. Taking a look at the truck it's easy to see the resemblance to an early '30s coupe, but it took Randy 3,000 hours of work over an 18-month period to get it that way. Randy chopped the Peterbilt's aluminum cab 5 inches in the rear and 8 in the front for the right rake before new aluminum was formed and riveted in place, just like the original, but much cooler. Additional metalwork was necessary to align the chop, including leaning the center post of the windshield back and contouring the bottom of the windshield opening to match the cowl. Up front, the Peterbilt 351 grille already had the nice, narrow width Randy was looking for-it just needed to be sectioned by 101/2 inches.

The majority of the truck's interior is Spartan-bare aluminum, but the handtooled, leather-wrapped bomber seats and saddle bags mounted on each door from GR Leather Products in Rogue River, Oregon, add a dose of color and texture. The only other adornment you'll find in the cab is a full set of Stewart Warner gauges in a Hollywood dash. Even the steering wheel and shifter knob for the four-speed Allison transmission are bare aluminum.

If you've ever seen the chassis of one of these Peterbilts, you'd quickly realize it doesn't have the aesthetics or the geometry for a custom, chopped-top hot rod. To solve the problem, Randy built a custom chassis for the Pete' using 3x6-inch, 1/4-inch-wall tubing. The frame had to hold up to the abuse of the massive, 4,500-pound engine Randy had in store for it, so it is beefy in all the right places. For example, the front crossmember is a solid, 11/8-inch plate, not tubing. The front suspension is made up of a GMC I-beam, a 7,000-pound-rated GMC leaf spring mounted transversely, and a set of radius rods. Randy couldn't find a chrome shop that would smooth his narrowed front axle, so he spent hours prepping it for the nickel plating that gives the metal a characteristic glow. Randy worked with Baer brakes to get enough stopping power and to ensure everything would fit with his drag racer-inspired 20-inch spindle-mount 12-spoke wheels that he had custom-machined from two 375-pound blocks of billet aluminum. The rear is just as sturdy, with a narrowed, centered, nickel-plated Rockwell axle filled with 2.67:1 gears. The axle rides on quarter-elliptical leaf springs that slide on bushings on the axle, and a triangulated four-link. Since the rear axle was a little more common, off-the-shelf semi Bendix brakes were used.

Finally, there's the engine. Sitting out in the open, for all eyes to see, is a gorgeous '74 12v-71 Detroit Diesel with two 6-71 superchargers perched atop the valley. For those of you who aren't familiar with the classic diesel engines and superchargers, the "71" in both of their names comes from the displacement of each cylinder, so the total displacement of the V-12 is 852 ci, or 14L. A 6-71 supercharger produces enough air to feed six 71ci cylinders, so, naturally, this V-12 would need two. In fact, everything underneath the bug catchers-from the superchargers to the oil pan-is stock, albeit much cleaner and more polished than you've ever seen before. The 71-series engines are two-stroke, so the superchargers are a necessity to fill the cylinders with air at just over atmospheric pressure. What isn't stock on the engine is the amazing exhaust. Initially, Randy built a set of zoomies to go with the dragster theme, but now he's got a perfectly polished set of 6-into-1 stacks that flow better with the overall look of the truck and boost performance as well. We've heard both versions, and we'd be hard-pressed to pick a favorite, as the exhaust from a two-stroke diesel as it revs to 2,800 rpm is like nothing else. It's smooth and balanced, but at the same time brutally powerful, and with a power stroke at every cylinder on every revolution, it sounds that much more angry. Even running practically zero boost, the engine produces nearly 475 hp and 1,200 lb-ft of torque. It's enough to make every gearhead within half a mile perk up and take notice.

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