Super A low oil pressure

I have been working on a super a for a while now, the block was cracked and I was ready to give up. a lady sold me a rebuilt engine out of a super C her husband (soon to be X) had lost interest in. The super C engine had new high compression pistons, was bored out and had fresh valve job very nicely done.I saw no sign of the bottom end being touched. I put the engine in the tractor and had low oil pressure. dropping down into the red zone when it is warmed up. here is what I have done,
1.I put the oil pump off my old super a engine with the cracked block on (that always had good oil pressure) and still had low oil pressure.
2.I pulled the pump apart and tried sanding the cover flat and putting a .001 gasket into it. Still low.
3.I took the rod bearings out and the mains that I could get to out and they rod bearings looked bad. The crank measured good so I put the bearings out of my old super A engine into it. They measure good and the clearance is within book specs. Still have low oil pressure.
4.I took the oil filter off and using a punch tried to shut the hole in the bolt a little to slow the flow down through the shunt oil filter. Still low but a little better.
5. I switched the gauge from my old super a onto the super c engine thinking maybe I had a bad gauge. still low.


my question is for you guys with a lot of C113/C123 experience. Is there a plug in the end of an oil gallery or in the valve train that could be
out letting my pressure just dump off? any other ideas?

some one else will jump in, however, that engine, in these parts, ran a low oil pressure.

There are no cam bearings, so that is not the issue. the upper end is lubed from the cam turning in the block letting a spit of oil go to the top end through a drilling. to the rocker shaft. No problem there. There could be a oil gallery plug in the inside of the block that was left out, Not sure if there is. Use 15 40 diesel grade oil in the engine, 10 30 is too thin. Jim

Mine runs at 30 to 50 pounds. Do you call that low?

Mine use to be low also, until i put new bearging's on the crankshaft,now it now pegs the needle!

You only replaced the mains you could get to, right? So there could still be loose mains letting the pressure drop.

If an oil gallery plug was missing it would have low oil pressure from the get-go, not drop as it warmed up.