Oldsmobile Lifter Bank Angles
While most engine families carried the same lifter arrangement throughout the series' production run, Olds engines were produced with some unusual variations in lifter bank angle, and even variations in the lifter size itself. Blocks were cast with two distinct lifter bank angles: 45-degree and 39-degree. This is important to note, since a camshaft must be ground specifically for the geometry of the block's lifter bank angle, meaning camshafts cannot be swapped from one type of block to the other. Another quirk is that the blocks were manufactured with two different lifter diameters-some were machined for .842-inch lifters, while others were made to accept unusually large .927-inch lifters.
So which engines got which setup? Initially, the Olds engine began with the 45-degree bank angle and .842-inch lifters found on the first year's production 330-cid engine in 1964-a setup retained in the 330 through 1967. The 400 began in 1965 with the same 45-degree/.842 combination, but changed to the 39-degree angle and .927-inch lifters for 1966 to 1967. Likewise, the 425 began in 1965 with the 45-degree/.842 combination, but for 1966 to 1967 it was produced with either the 45-degree/.842-inch or the 39-degree/.927-inch arrangement. The latter is said to have been used primarily on the 425 engine in the premium Toronado model. For 1968, the 39-degree lifter bank angle was standardized across the board in all Olds engines. Where the 39-degree lifter bank angle had previously been used only with the large lifters, the '68-and-later engines all used the 39-degree lifter bank angle with the smaller .842 lifters.