Todd,
I am not certain if the information below is correct for the 1953 Powerglide auto engine but I think it is.
The picture that you posted of the distributor side of the block has a side cover (push-rod cover) for a high pressure 235 (and 261). The earlier 235/216 had a side cover that extended over the spark plugs. The head on that engine is also from a later 235 (or 261) - it has a later valve cover.
Regarding "full-pressure oil". The commonly used (and confused) terms for the oiling systems in 216/235/261 engines are:
low-pressure oil system: a feature of all 216s and all pre-54 235s, except for the 1953 Powerglide 235. These low-pressure oil system engines had a different head from the later engines and they had a valve cover that is held down by two bolts. I think these low pressure engines had some sort of small triangular plate/cove on the exhaust side of the block (this is another characteristic that distinguishes this block from the later block).
high-pressure oil system: refers to the 1953 Powerglide 235 and all 1954 and later 235/261 engines, which had a high-pressure oil system (and insert rod bearings, rather than the earlier babbetted bearings). All of these heads (except the '53 Powerglide?) had valve covers that were held down with four machine screws (they look like stovebolts).
by-pass oil filtration system: an option/accessory available for almost all low-pressure and high-pressure 216/235/261 engines. I believe that about 10% of the oil was diverted through the by-pass oil filter. This might seem odd but it does work fine.
full-flow oil filtration system: only used on 1958-1962 Chevrolet truck 261 engines (Canadian Pontiac 261 engines did not have a full-flow filtration system). GMC engines, which are in many ways superior to the Chevrolet engines, did not have a full-flow oil filtration system. The easiest way to identify these engines (besides using block casting or block/engine ID codes) is to look at the size of the oil filter hose-fittings on the exhaust side of the block - the full-flow 261s holes for the filter hoses are 1/2" NPT (looks like a 3/4" hole).
The term "full-pressure" oil system might be used to describe the high-pressure 236/261 engines but the term can be confused with "full flow" ("full pressure"?) oil filtration system on some 261 engines.
So, regarding your question ". . full pressure oil, would there be any outside indication?", the short answer is "yes". The push-rod side cover is one giveaway of a high-pressure engine and the triangular plate/cover on the exhaust side of the block is another giveaway. There are also external giveaways/characteristics to identify full-pressure(high-pressure)/full-flow oil-filtration systems (on 261s or 235s that have been adapted - see
Tech Tip ).
If I have stated or described anything incorrectly or unclearly, we can be certain that people will post corrections.
Good luck,
Tim
