Prior to 1953, the 235 engine had the lower-pressure engine lubrication system which was used in all 216 engines, compared to the later 235 (and all 261) engine's higher-pressure lubrication system. Two significant changes in the engines were that the lower-pressure engines had babbitted (non-inert/non-removable) rod bearings that were not lubricated with pressure-fed oil delivered through the crankshaft.
1953 was a transition year with respect to the 235 engine. With respect to oil-lubrication, the 1953 Powerglide car 235 engine was the first 235 engine with the higher-pressure lubrication system. The other 1953 car 235 engines and the 1953 truck 235 engines still had the lower-pressure oil-lubrication systems.
There are several other oddities in the 1953 235 car and truck engines - here are a few significant oddities:
- 18 head bolts in all blocks/blocks compared to 15 head bolts in all 216 blocks and all earlier 235 blocks/heads. All 54-53 2235/261 heads/blocks had 18 head bolts.
- 2 bolts hold the 1953 valve cover to the head and this is the only year that 18 bolt head had a 2-bolt valve-cover attachment (4 machine screws on the sides of the valve cover were used from 54-63).
- I think that the same 18-bolt block was used in all 1953 235 engines, making it the only 18-bolt block used with a low-pressure lubrication system (on manual transmission car 235s and on all truck 235s).
- there are other, subtle but important, differences.
(pre68dave and others will correct any of the above, if necessary)
