Oil press mystery

What’s the number on the filter?

(I cut my teeth running a tug with a 1937 Atlas Imperial that had been sunk more than once)

Keep it aimed at something cheap…

yes, thru the 3/4 or 1" nipple! right into the filter… (s), just not OUT of it!

Seems to me that oil delivered from the pump to the filter should be entering into the outside holes to the outside of the filter element, with clean oil continuing it’s journey to the crank and elsewhere from the center hole. On many spin-on filters, you can look down the center hole and see a valve, then,on some brands specced for the same application, it may not be there. Cheaper. I’ve seen it many times on the Fram PH14 equivalent filters. Your poor flow issue may be a result of a filter brand idiosyncrasy. On many small engine oil supply pumps, there are also pressure relief valves, but yours appears to work and is set at 40lbs. if the gauge works correctly, but don’t take that for granted. I’ve seen gauges lie.

some good ideas coming on here!, normally the oil goes into a filter in the center and such is the case here. one filter is a stp filter and the other is a fram. both new… and i never looked inside either of these but sure will be doing that! one of the prev. commenters said possibly the filter adapter block was on backwards which is the most appealing idea yet except for the obvious fact the filter adapter housing has been on this engine for years as is and yes, i removed it anyway and had a look at it and it is a ‘‘see thru’’ aluminum block with no surpises.
I’ll get to it eventually but for now this has to set on the sidelines while i rebuild a detroit i screwed up 3 years ago and i have 200 acres to irrigate daily, a sawmill to get on a job, fences in constant need of repair and a hundred other distractions!

“normally the oil goes into a filter in the center”
I wouldn’t normally argue the point, but it could have a bearing on the issue:
https://www.google.com/search?q=oil%20filter%2C%20how%20it%20works

It is possible that your setup worked with a particular brand of filter that did not incorporate an anti-drainback valve, as seen as item 2 in the picture:

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I would start at the oil pump itself and inlet screen. Make sure the screen is clear, the gears are not worn, and no leakage through the relief valve below the set value.

well this project is on hold. I’ve two other engines but this will prob go into my new shop and get a fast frame up inc. the engine!!