The Stovebolt Site Forums The Shop Area Engine Shop diference between 55 and 56 chevy 235

1955 and 1956 235 block difference Taken from the 1956 Truck Supplement to the 1955 Manual

The dowel in the upper half of the precision main bearing has been discontinued for 1956. A tang is provided at the butting edges of the new upper bearing. The tang ,which registers with a slot in the cylinder block and locates the upper bearing, also butts against the bearing cap to prevent rotation of the bearing. The adjustment shims formerly used between the bearing cap and cylinder block have also been discontinued. With the new tanged bearing and elimination of shims, dropping of the crankshaft in “Main Bearing Replacement” is unnecessary and “Main Bearing Adjustment” is eliminated for the 1956 engines. Whenever main bearing are checked and excessive clearances found, new bearings should be installed.

All 235 truck engines had mechanical solid lifters and I think aluminum cam gears. The cars with power glides had hydraulic lifters with a fiber cam gear.

Maybe it has to do with the distributor gear there were 2 styles I forgot which year was what but I think the camshaft was either steel or cast iron.