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The clueless, me, would switch out the oil pressure sending unit, if it is electrical on a 38, with a new one or another old one and see if the reading is consistent. That pressure should change across that range.

Finally got around to testing the oil pressure and chasing down the leaks at the oil filter housing. I took the car back to Colvin Automotive, since KC has a nice kit with gauges, fittings and quick release hoses. With a warm engine (160 on the temp gauge), the accurate gauge shows 24 lbs at idle and 48 lbs at a little over half throttle.

So, the answer is the dash gauge is not accurate. For now, we are leaving the gauge un-repaired. It will act like a trouble light. If it shows 50 lbs, we have oil pressure. If it shows a low oil pressure, we have a problem.

As for the leaks at the oil filter housing (a reproduction unit from Max Merritt), there were two sources. The first was the seal between the top and the housing. The seal supplied was too small in diameter and the ring edge two wide. It would not sit flat in the edge recess, and thus was making only partial contact with the top rim of the housing. A new seal was sourced from an automatic transmission repair kit that fit perfectly.

The second problem was the bolt that secures the lid to the housing. This is a standard 7/16" bolt with a 5/8" head. Although two fiber washers and a regular washer were supplied, oil was still coming up along the bolt shaft and exiting under the bolt head and over the metal washer. To solve this problem, KC welded a wide diameter washer below the bolt head, creating a 'flange head' bolt. The bottom of the washer was then turned on the lathe to ensure true flatness. To secure the filter top to the housing, we used the two provided fiber washers, followed by a 7/16" copper crush gasket, and then our 'flange' bolt.

No more leaks.

Thank you all for your help.

Tom

Tom, Good trouble shooting. Glad to hear there were no problems with the engine, just the gauge and gaskets. You should be able to sleep better tonight.

(o[]o)