by Tommy Lee Byrd
Big cars like Randy’s Grand Prix rarely garner attention from hardcore car guys because the additional weight is generally a disadvantage. While the full-size Pontiac is hefty at 4,150 pounds, the immense power is a great way to make a sleeper out of a car built in the muscle car era. (Photo courtesy Kyle Loftis)
If you bought a new Pontiac Grand Prix in 1970, you probably didn’t take it to the drag strip that often. You could get one of these cars with a 370-hp Pontiac block under the hood, but when you consider the 4,150-pound curb weight, the combination didn’t equate to very quick elapsed times at the track. The rather large platform never lent itself well to the performance-minded fellow, so it’s a great sleeper platform, even though it was introduced at the peak of muscle car performance. Randy Belehar of Detroit Lakes, Minnesota, owns this particular car and it bears a completely stock appearance, down to the Pontiac Rallye II steel wheels. It does, however, boast a pair of Mickey Thompson 315/60R15s, but that’s the only sign of this car’s potential.
Randy bought the Grand Prix in 1996, and it was actually his first car. He was 17, and drove the car to his Senior Prom, never dreaming it would turn out the way it did. He raced it for nearly a decade, running it in total beater form, with primer and rust taking over the car’s original paint job. Randy says, “I tore it apart in 2007 to fix the rust in the floor, and it snowballed into completely redoing the whole car.” He did an awesome job with it, while keeping it very clean and simple—a perfect combination for a quality sleeper.
Since the rebuild, Randy has competed in Hot Rod magazine’s Drag Week competition, a week-long, 1,000-mile journey to various drag strips. The car has never gained a ton of recognition because of its tame looks, but it’s a great car that exemplifies the full-size sleeper look. The source for horsepower is a 1975 Pontiac 455 block that now comes in at 467 ci, thanks to a slightly longer stroke and a .030-inch overbore. It’s a healthy combination that looks relatively mild mannered, so it certainly works with the sleeper theme.
The 467-ci block features an Ohio billet crankshaft, which slings a set of Eagle 6.8-inch connecting rods and Ross pistons to a maximum RPM of 6,700. Atop the forged short-block is a pair of Kauffman aluminum cylinder heads that flow 325 cfm, thanks to the very efficient D-port design, which sends a perfect mixture of fuel and air into the combustion chambers. The valves measure 2.11 inches on the intake side and 1.77 inches on the exhaust, while a set of Crane 1.65:1 roller rockers keeps the valvetrain moving smoothly. The camshaft is from Comp and it’s a solid roller, which features 254 degrees of duration on the intake and 260 degrees on the exhaust—both measured at .050-inch lift. Max lift on the camshaft is .669 inch, and it was ground on a 110-degree lobe separation angle.
A port-matched Edelbrock Victor Jr. intake manifold rests on top of the big-block Pontiac, and is finished off with a Proform 850-cfm carburetor. Although the 467-ci engine proved its potential by making 460 hp and 580 ft-lbs of torque to the rear wheels on the motor alone, Randy’s secret weapon is a two-stage Big Shot nitrous system from NOS. The car features a separate fuel system, which consists of a 1-gallon fuel cell filled with 110-octane race gas, to feed the nitrous system, while the engine is fed with 91-octane pump gas. After pouring the coals to it on the dyno, the result was 642 hp and 660 ft-lbs of torque to the rear wheels. That means the Poncho big-block is making around 800 hp at the flywheel. To support all this power, Randy relies on a Summit 140-gallon-per-hour fuel pump and an Accel HEI (high energy ignition) distributor, which is assisted by an MSD Digital-6 ignition box. Randy isn’t trying to hide anything, in terms of the car’s exhaust note, as it beats the ground with Pypes race mufflers and 31⁄2-inch pipes.
Behind the block is a Cottman Transmission–prepped TH400 automatic, which is outfitted with a Continental 10-inch torque converter and a host of bulletproof components to keep it together for long trips like Drag Week. Another part that plays into the long trip aspect of this car is the Gear Vendors overdrive, which makes the 3.73:1 rear end gears seem a little less aggressive at highway speeds. The rear end is a GM 12-bolt, packed with an Eaton Posi unit from Tom’s Differentials and Mark Williams 30-spline axles. Rear suspension is the stock triangulated four-link design, fit with adjustable upper and lower control arms, as well as 14-inch 130-pound springs and QA1 single adjustable shocks. The only modification to the front suspension is the 260-pound Moroso springs and QA1 shocks. Randy equipped the Grand Prix with a set of Rallye II wheels, measuring 15x7 inches up front and 15x10 inches out back. The rears are wrapped with Mickey Thompson 315/60R15 drag radials, which required Randy to notch the rear frame rails for clearance.
Shayne Laske installed the 10-point chrome-moly roll cage, and did an awesome job hiding it by tucking the tubes very close to the body structure. The interior is all stock with the exception of RJS harnesses and a B&M shifter. The green exterior is just right for the sleeper look, and the vinyl top adds a luxurious touch to the full-size two-door. Just about anyone’s grandmother would’ve been proud to drive a 1970 Grand Prix, and Randy is proud to leave many cars in the dust as he makes a 9-second pass in the quarter-mile. So far, his best elapsed time is a 9.91 at 133 mph, running 6.26 to the eighth-mile, and the car runs solidly in the low 11s without the nitrous. It’s a great looking car, and while it was built in the muscle car era, it’s a dead on sleeper, especially on the drag strip.
Randy’s full-size Pontiac is yet another car from the muscle era that would normally be considered a moderate performance car on the street. On the track, however, Randy’s stock-appearing Poncho proves it’s not a stocker by blasting off high-9-second passes on a regular basis. (Photo courtesy Kyle Loftis)
Taken from Tommy Lee Byrd's Street Sleepers published in 2011