Diesel 871 with low oil pressure

My 871 runs at about 40lbs until the engine warms up. Then it begins to drop down to about 10lbs. I have 30 weight oil in it. When we did the rebuild we didn't see any problems with the pump or the pickup. Any ideas?
 

usually symptom of worn out mains and inserts.... what did the overhaul replace? Did you check the rod and main bearings for sizes and wear? Did you plati-guage them or mic the surfaces? Did you replace the bearings?
 

Just for reference, my '64 4000 diesel pegs the pressure gauge until it gets warmed up. It then runs about 40 psi around 1600 RPM or above, maybe slightly more at higher RPMs. I'm running 15W-40 in it.

I'm guessing you have a leak somewhere. or too much clearance as Fordfarmer suggests.
 

Did it have the aluminum oil pump, if so replace it.
My 881 has only 3200 hrs but the oil pressure is down to near your levels, my plan is to replace the oil pump first, the early pumps didn't pump the amount of oil nor make as much oil pressure as the later pumps
 
Try a good 15-50w oil these engines were hard on mains Ford used hard bearings causing crank wear in these diesels usally requiring the crank to be turned when overhauling.
 
I am in UK and some years ago I know someone that overhauled the engine in a IH 454 diesel,the crank was machined and a new oil pump was fitted and when the engine was started the oil pressure was good until it warmed up then it went down to nearly zero...it was dismantled again and the cam shaft bearings were renewed then afterwards there was very good oil pressure
 
I've rebuilt/repaired a bunch of these engines and most of them have the ears warped on the pick-up tube or the pressure tube where they bolt
to the oil pump. If these ears are bent/warped it will suck air on the pick-up tube or loose pressure on the pressure tube. I usually use a
vice and hammer to bend the ears back into shape. Next, many of these have had the nut holding the pressure tube to the block tightened too
tight on the grommet causing the tube to be compressed enough to distort the tube and restrict the oil flow to the filter. Be sure your
pressure tube has a new or good grommet on the tube or in the block before you finish this job. As others have mentioned you need to check
bearing clearance and be sure the oil pump is up to snuff.
 
(quoted from post at 18:45:43 08/27/18) I've wondered about the oil. Is 30 too light for north Nebraska except in the winter?
30 should be fine for a tight engine until it gets colder. Then you'll want a10 or 20 if you're sticking with a straight weight

Personally I'd put Archer's Extra-Life 15W-40 in it and not worry about changing it for winter . . . unless it gets below 0 and stays there for a while.
 

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