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The Pontiac Tempest


Road-Racing Tempests
Perhaps even more obscure than the drag racing Super Duty Tempests were even fewer 421-powered Pontiacs that made their way onto to road courses and oval tracks soon after Mickey Thompson's cars began invading America's dragstrips. Four cars were prepared by Nichels Engineering (in Indiana) for the inaugural NASCAR Daytona Continental sports car race in 1962, but only one finished.

Pontiacs returned to Daytona in 1963 with a strong car entered by Nichels and driven by Paul Goldsmith. In a wet Daytona American Challenge Cup race on the big oval, the little Pontiac bested a Mystery 427-powered 1963 Corvette owned by Mickey Thompson, a Cobra, and other import cars, including a Ferrari. The next day, in a contest called the Continental Cup race, the Tempest unfortunately retired with what was later attributed to driveline failure.

Goldsmith's number 50 car used the similar twin four-barrel 421 Super Duty engine but retained the intriguing four-speed Powershift factory transaxle assembly. This design used a clutch located at the very back of the transaxle but only employed it to launch from a dead stop. Once moving, all gear changes were made without the use of the clutch by merely moving the gear selector, although shifting in this manner probably contributed to the early transaxle failures. Major suspension changes had been applied to the original swing-axle design to improve the handling, and the car was clearly competitive. Unfortunately, this factory-enhanced effort was discontinued soon after the Daytona race in deference to Washington, D.C. sabre rattling.

The Super Duty 421
The 421 Super Duty took Pontiac's very successful 389 and made it bigger all the way around. They increased the bore by 0.030 inch to 4.093 inches and added a 0.250 inch to the stroke for a total of 4.0 inches. The first 421 Super Duty appeared as a dealer-installed engine in 1961, followed as optional engines for the Catalinas and, of course, the SD 421 Tempests in 1963. In that year, there were three different Super Duty 421 configurations. The single four-barrel version was factory-rated at 390 hp, sported 12:1 compression, and was intended for NASCAR stock car racing. Adding another carburetor to the same engine pushed the second version to 405 hp. Pontiac's big dog in the factory horsepower hunt retained the twin four-barrel induction but added another point of squeeze to 13:1. Rated at a ridiculously conservative 410 hp (500–550 hp is more realistic), this engine was intended for drag racing.

All SD engines were equipped with forged crankshafts, forged pistons, and 3.250-inch main journal diameters, increased over the 389's already large 3.00-inch journals. Rod journals remained the standard Pontiac size of 2.250 inch. Four-bolt main caps were also standard. Iron Super Duty cylinder heads (the 980 head carried the late 1962 and 1963 casting number, while earlier 1962 engines received 127 heads) and to keep the inlet air temperatures cooler, both units were built without the usual heat-riser passage. All SDs also came with one of three mechanical lifter camshafts, referred to as McKellar cams, in reference to Pontiac chief powerplant engineer Malcolm "Mac" McKellar, who was responsible for their lobe designs. McKellar also designed not just camshafts but also oversaw the creation of the SOHC inline-six and many of the exotic DOHC engines that Pontiac experimented with in the late 1960s.

The Super Duty 421 engines also spawned a number of interesting factory-inspired performance components. If you were connected to the pipeline in 1963, you might have scored one of perhaps as many as 40 or 50 two-piece "bathtub" tunnel ram intakes cast by Pontiac. Other unique pieces included a three-barrel Carter AFB carburetor (PN 3636S) intended for NASCAR circle-track engines. Due to the GM corporate ban of late January, 1963, all engine production halted. While successful in killing Pontiac's factory support of racing, this performance ban would last only a few months until Pontiac again pushed the envelope with the more street-worthy '64 GTO.

More Info
Pete McCarthy Publications; 714/997-5856;
Little Indians Chapter of the Pontiac Owners Club, International;

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