A belt-driven Overhead Cam (OHC) engine of 230 and 250 cu. in. displacement, was offered from 1967 to 1969. It uses a cast iron block and head, and was available with a 1 or 4-bbl. carburetor. A unique feature of this engine was the accessory drive housing assembly located on the front, right-hand side of the block containing the oil pump and filter, fuel pump, and distributor. The assembly is driven by the timing belt.
The overhead cam 6-cylinder engine was replaced by an overhead valve, 250 cu in. 6-cylinder engine in 1970. It has a cast iron block and cylinder head, uses hydraulic valve lifters, and is basically the Chevrolet 6-cylinder engine.
In 1967, the 326 cu in. V8 remained in the engine lineup, but the old 389 was replaced by the new 400 cu. in. V8. In 1968 and 1969, the 400 engine was retained, although the Ram Air version of this engine was given four-bolt main caps due to the increased performance. In 1968, an all-new 350 cu. in. engine of Pontiac design was introduced. This engine is used as the standard base V8. The 455 cu. in. engine became available in the Firebird in 1971. The basic engine lineup remained the same through 1974 with modifications for emission control and a concurrent reduction in power output.
Beginning in 1977, three new engines were added to the Firebird line-up. The 250 6-cylinder engine was discontinued in favor of the Buick-built 231 V6 engine. This engine is a cast iron, overhead valve V6. Its crankshaft rides in four main bearings with the thrust being taken by bearing No. 2. These engines are known as `Even-Fire' engines because the cylinders fire at equal 120ordm; intervals of crankshaft rotation.
A 301 V8 was introduced and was basically the 400 V8 with smaller pistons. 1977 also signalled the end for the once formidable 455 V8; the engine to take its place, the 403 V8, was simply a 350 with a different stroke and cylinder bore size.
In 1978, the 301 V8 was temporarily replaced by a 305 V8 due to availability problems. 1979 engines remained the same, except that the 301 was again included.
In 1980, the energy crisis being what it was, the 350, 400 and 403 V8 engines were all dropped in favor of the smaller, fuel efficient 301 and 305 V8s. In addition to these two, an even smaller V8 was added, the 265. Also in 1980, Pontiac introduced the turbo-charged version of the 301 V8, to meet the demand for a fuel efficient high performance engine. The engine is basically a standard 301 equipped with special heads, low compression pistons and modified intake and exhaust manifolds in order to accommodate the turbocharger.