No if the 55 was originally a stick motor. 55 engine blocks came in two flavors, mechanical lifter only blocks for the stick shift motors and hydraulic lifter blocks for the powerglide equipped motors. The mechanical lifter blocks are not drilled with the oil galley needed to feed hydraulic lifters so those style blocks can only be run with mechanical lifters. The hydraulic lifter blocks can be used with hydraulic lifters or retro fitted with mechanicals. The distinction between the blocks ended after the 55 model year, so for cars From 56 forward, hydraulic lifters on all of them. Trucks are a bit of a toss up because so many motors have been replaced over the years that you rally have to look at the block to see if it’s been drilled or not.
As for the rocker assembly, in 59 gm made the last of the improvements to the 235 and 261 motors including a change in the oiling to the rockers and the rockers themselves. Instead of the steel line that runs from the rear cam bearing to a boss at the underside of the the middle top of the block, the 59-63 motors had a dedicated galley drilled from the main oil galley through the block to the head. The 59 motors had a larger oil oraface drilled in the block passage to the rockers to allow more oil and pressure to the rockers then the prior 55-58 design. The connector for the rocker shafts was also different in that the copper line was crimped off and the system created a sort of pressurized oil to the rockers. The 55-58 connector was open and looped excess pressure back to drain into the head and then the pan.
As you know, the rockers must dribble, not spit, oil. The 55-57 low pressure rockers did this through the dribble hole. If you look at the inside of a 55-58 rocker arm, you will see a small oil groove that directly intersects the dribble hole. If you were to use this rocker on a 59 and up motor, the higher pressure would cause the rockers to spit and not dribble so less or no oiling to the rocker tip, the ball and seat of the adjuster and push rod, and no oil to cool and lubricate the springs and valve stems because the oil was spitting over the important parts that needed lubricant. To solve this issue in the 59 and up motors, gm offset the grove in the rocker so that the added pressure and volumn would assist in getting sufficient oil to and through the rocker shafts, and the offset groove in the rocker arms would restrict the oil to a dribble out of the dribble holes. So, long story I know, but that is why you should not use the 59 rockers on a 55 block, you will starve the top end of oil. Not enough pressure and volumn to over come the offset groove in the rocker arms.
To be complete, let’s say you wanted to use a 59 block with the 55 head and rockers. That would produce too much oil and pressure to the rockers. Gm recognized this issue when it stopped supplying replacement blocks and short assemblies for the 55-58 vehicles. To use a 59 and up block with a 55-58 head and rocker assembly, gm devised a plug and drilled bolt arrangement that restricted the higher pressure and volumn of the 59 block so that you could use that block with the earlier heads.
As for the push rods, quite a few of the mechanical lifter 55 motors came with the old style milk bottle type of lifter. Later 55 stick blocks came with the more recognizable style of lifter. The milk bottles were taller and thus used a shorter push rod then the later lifters which were shorter. So if the 55 motor has milk bottle style lifters, the the push rods from the 59 motor are too long.
Let me see if I can dig up a few parts and take a few photos.
Last edited by Dragsix; 11/25/2018 5:16 PM.
