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The Pontiac Tempest and the Four-Cylinder Engine
One of the many innovative decision John Z. DeLorean brought to the Pontiac Tempest was the four-cylinder engine. Though the Buick and Olds Y-bodies would be powered by a choice of newly designed V-6 or aluminum V-8 powerplants, DeLorean's engine of choice for the related Pontiac was going to be an inline four. It would have to be more powerful than competitive sixes and be inexpensive to develop and manufacture.
Indeed, Pontiac was truly up against the wall with respect to cost. With the majority of developmental funds tied up in the unique drive-shaft system, the rest of the driveline would have to consist of as many off-the-shelf pieces as possible. DeLorean and his team determined that a four-cylinder based on the production Pontiac V-8 would make the most sense.
In order to prove that the concept was valid, engineers took a production 389-cid Pontiac V-8 engine, put holes in the left bank of pistons, disabled the valve-train for the same cylinders, and reinstalled it in a full-sized Pontiac. Even with the extra drag of the deactivated cylinders, the cobbled-up test engine had enough steam to propel the 4,000-plus-pound sedan to a top speed of 92 mph and still give satisfactory gas mileage.
Later, the left banks of several production 389 engines were removed. A series of specialized parts were then developed for production, including a specific crankshaft, camshaft, two different intake manifolds, a four-cylinder ignition system, and various downsized accessories. The production 195-cid ohv "slant-four" block came a bit later. It was heavy, weighing about two-thirds as much as the V-8 because the 389's crankcase was retained almost unchanged.
The good news was that interchange-ability with the 389 abounded. The two engines shared pistons, rings, pins, connecting rods, bearings, cylinder heads, oil pan and pump, water pump, crank pulley, and harmonic balancer. The four also used the same machine tooling and traveled down the same assembly line as the V-8, greatly reducing manufacturing cost.
All told, there were three basic versions of the "Trophy 4" engine for the 1961 model year. The first was a regular-fuel engine with an 8.6:1 compression ratio and a one-barrel carburetor. It was rated at 110 bhp at 3,800 rpm, with 190 pound-feet of torque at 2,000 revs. For automatic-transmission cars, this engine was rated at 130 horses at 4,400 and 195 pound-feet of torque at 2,200, thanks to a hotter camshaft than that used in the stickshift cars.
The second version retained the single-throat carb, but compression was raised to 10.25:1, necessitating the use of premium fuel. The manual transmission version was rated at 120 bhp at 3,800 rpm and 202 pound-feet of torque at 2,000 spins; the automatic version made 140 bhp at 4,400 rpm and 207 pound-feet at 2,200.
The raciest iteration of the four was equipped with a Rochester four-barrel carburetor and an even hotter camshaft. Both sticks and automatics were rated at 155 bhp at 4800 rpm, generating 215 pound-feet of torque at 2,800 revolutions. Buick's 215-cid V-8 was also available. Fitted with a two-barrel carb, it also was rated at 155 bhp, but generated slightly more torque at 400 fewer rpm than the meatiest four.
Though the Tempest had plenty of power, the engineers at Pontiac had to next consider how the car handled. On the next page, learn what made the Pontiac Tempest such a smooth ride.For more information on cars, see: