The timing chain in the Trophy 4 was originally the same as the 389, but was prone to stretch and break from engine vibration a special high-strength version was developed as a replacement. The Trophy 4 is instead cushioned by flexible rubber engine mounts designed to isolate the engine from the rest of the car, and its forces are further damped by the Tempest's unusual drivetrain that distributes these forces through the torque tube to the rear-mounted transaxle. Modern engines larger than 122 cu in (2.0 L) tend to have twin counter-rotating balance shafts to counteract these vibrations, but balance shafts were not commonly used until the mid-1970s.
Due to the geometry of the wrist pins, connecting rods and crankshaft journals a piston descending from top dead center will always move quicker through the first 30 degrees of crankshaft travel than a piston moving upward from bottom dead center, meaning that more mass is moving downward than is moving upward, causing a shaking in the vertical plane. The two outside cylinders move together simultaneously, as do the two inside cylinders. The curve of this flexible, thin driveshaft earned it the nickname "rope drive".Ī downside of the Trophy 4 is engine vibration, as an inline four-cylinder engine suffers from inherent secondary imbalance resulting from its 180 degree crankshaft. Uniquely, the shaft is also bent downwards into a curve, which has the effect of making the critical speed of such a flexible shaft higher than the engine's maximum rpm. This allows it to be an unusually small 5⁄ 8 inch (16 mm) solid rotating shaft, inside the pressed steel square torque tube. As the driveshaft runs at engine speed, rather than the transmission output speed, it runs at a higher speed and lower torque than a conventional driveshaft for a rear wheel drive car. The Tempest's drivetrain features a rear-mounted transaxle connected to the engine via a torque tube, giving the car a near-perfect 50-50 front-rear weight balance. A "power pack" option for the 1962 four-barrel carburetor increased rated power to 166 hp (124 kW).
63 PONTIAC TEMPEST MANUAL
The brainchild of auto industry legend John DeLorean, then the head of a design team responsible for the birth of the Tempest line, the Trophy 4 produces 110 hp (82 kW) ( gross) at 3,800 rpm and 190 lb⋅ft (258 N⋅m) at 2,000 rpm with a single-barrel carburetor (as fitted with manual transmission using regular gas, and 120 hp (89 kW) with premium) 130 hp (97 kW) with regular gas (and 140 hp (104 kW) with premium), as fitted with automatic transmission and 155 hp (116 kW) at 4,800 rpm and 215 lb⋅ft (292 N⋅m) at 2,800 rpm with the optional four-barrel carburetor and automatic transmission. The Trophy 4 weighs about 470 lb (210 kg), as compared to the 650 lb (290 kg) V8 it was based on. This degree of commonality enabled it to be produced on the same lines as the V8, allowing substantial cost savings. It shared most of the 389's tooling and up to 120 of its parts. The Trophy 4 engine is a short-stroke, 45-degree inclined inline four created from the right bank of the 389 V8 for the debut of the Tempest in 1961. It was dubbed by Pontiac the Trophy 4, playing off the racing success that had earned the 389 V8 engine the nickname Trophy V-8 after just two years of competition.
Created from one bank of Pontiac's powerful 389 cu in (6.4 L) Trophy V8, its only application was in the first generation Pontiac Tempest. The Pontiac Trophy 4 engine (also called the Indianapolis 4, or Indy 4) is a 194.5 cu in (3.2 L) inline four-cylinder engine produced by the Pontiac Motor Division of General Motors for model years 1961 through 1963.
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