engines were very similar, using the same bore centers and a deck height, raised on "big-block" versions to . Big-block and Diesel versions also increased the main bearing journal to for increased strength. All generation-2 small-block Olds V8s used a stroke of . The big-block engines initially used a forged crankshaft with a stroke of 3.975" for the 1965-1967 425 and 400 CID versions; starting in 1968, both the and the big blocks used a stroke of , with crankshaft material changed to cast iron except in a few rare cases. These were wedge-head engines with a unique combustion chamber that resulted from a valve angle of only 6°. This was much flatter than the 23° of the small-block Chevrolet and 20° of the Ford small-block wedge heads. This very open and flat chamber was fuel efficient and had lower than average emissions output. It was the only GM engine to meet US emission standards using a carburetor all the way up to 1990. 330 The first second-generation Oldmobile V8 "Jetfire Rocket" introduced in 1964 and produced through 1967. It was released one year earlier than the tall deck 425, and debuted the standard stroke; bore was . 330s were painted gold and had forged steel crankshafts. The 4 barrel versions had a larger diameter harmonic damper, the 2 barrel only a balancer hub without the rubberized outer ring. 400 The version was the second tall-deck "big-block" Olds. Two distinct versions of the 400 CID engine were made: 1965-1967 "Early" 400s used a slightly oversquare bore and stroke for an overall displacement of . All the pre-1968 engines used a forged steel crankshaft. 1968 and 1969 400s shared the Olds big-block standard stroke with the 455 but used a undersquare bore to comply with GM's displacement restrictions in the A-body cars while also reducing tooling costs. Displacement is very close to the earlier engine, at . This "later" 400 is considered less desirable by many enthusiasts, because of the power band characteristics induced by this undersquare format, although the actual change in power was due to the mild 250/264 duration cam used in this engine (previous 400s used a 278/282 cam) and the fact that the crankshafts were now made of less durable high nodular iron material. "Early 400s" used the same forged steel crankshaft as the 425, while "later 400s" used the same cast iron crankshaft of the 455,