lusty1,
There is an old post on this topic but here is a brief run down:
1. The full-pressure or high-pressure oil system was first available in the 1954 235 and 261 truck engines. In 1953 the full-pressure oil system was used only in Powerglide car engines - this was not a truck engine and it had hydraulic lifters. Prior the 1954, all 216 and 235 truck engines were low pressure engines, with oil (rod) dippers for lubricating the rod bearings.
2. An oil filter was optional on all 216/235/261 engines. A full-flow oil filter was optionally available on only the 1958-1962 261 truck engine. A by-pass oil filter was optionally available for all other years and sizes of truck engines (from GM or Fram or others). In a by-pass oil filter system, only about 20% (?) of the oil flow is by-passed through the oil filter. In a full-flow system ('58-'62 261 engines) 100% of the oil flow went through the oil filter.
Thus, low pressure vs high (or full) pressure oil system refers to the lubrication system in the engine; and, by-pass vs full-flow oil filter refers to the optional oil filtration systems.
I think there is a link on the Tech Tips page for converting to a full-flow oil system.
Other things to note:
- A full-flow oil filter system can be replaced with a more modern spin-on oil filter (through use of a converter kit).
- A by-pass oil filter should not be installed on a '58-'62 261 engine.
Good luck. I am certain that others will correct me where/if I am wrong.
Tim
