All Pontiac and other GM-built engines covered in this guide-whether inline four, six, V6 or V8-are water-cooled powerplants with pushrod valve actuation. All engines use cast iron cylinder blocks and heads.
The 151 cu. in. inline four and the 250 cu. in. inline six are nearly identical in construction, the four being basically a six with two cylinders removed. Both engines have gear-driven camshafts, hydraulic lifters and pivot-type pressed-steel rocker arms like some of the V8s. The only major variation in these engines is the manifolding on the 151 four. The 1977 and 1978 151 cylinder heads have both their intake and exhaust manifolds mounted on the same side, while the 1979 engines feature a "crossflow" design with the intake and exhaust manifolds mounted on opposite sides of the head; this allows the engine to breathe much more efficiently.
The gasoline V8s are also very similar in construction, and share common design features such as chain-driven camshafts, hydraulic lifters and pressed-steel rocker arms. The Buick-built engines, including V6s, differ in that they have their rockers mounted on shafts. Because of this similarity between engines, many removal and installation procedures given here will simultaneously cover all GM-built engines used in mid-size Pontiacs. Likewise, the 231 and 252 V6 engines are nearly identical to themselves and to the Buick V8s.
The 350 V8 diesel is derived from the 350 cu. in. gasoline engine, except that the cylinder block, crankshaft and main bearings, connecting rods and wrist pins are heavier duty in the diesel (due to the much higher compression ratio). The diesel cylinder heads, intake manifold, ignition and fuel systems are also different from their gasoline engine counterparts. Aircraft-type hydraulic roller valve lifters are used in the diesel.