I decided to tear her back down and replace the oil pump.
Please keep us posted. If what is bothering you is what I think, you are probably wondering about the clearances between rod and crank journals in the new bottom end.... and also whether the oil pump itself is worn. Did the pressure go up rapidly when rpms were increased? To my mind that would indicate pump wear, but you won't really know until you compare with a new pump.
In the past I've found that just what restriction you are measuring with the the oil gauge pressure depends a lot of where the oil line is tapped for the pressure reading. It's pretty common for the gauge to tap into the flow somewhere between the bottom end and the valve gear, but that means the pressure you read is influenced by how restricted the flow is to in the upper end & valve gear. Another source of pressure loss is that some diesels in that era had a sprayer nozzle in the crank sump for each cylinder that shot a spray up toward the inside of the pistons and the lower cylinder area. I don't know if the Ford 2110 has that. If so, check the sprayers
I'd probably do just what you are and replace the oil pump just to see if it makes a difference. Even though I'm not sure what I'd do with the information either way. What are you thinking?
After all, crank and rod bushings are said to ride on a dynamic wedge of oil created by the crank rotation. All the oil pump does if that is true is to feed enough oil in there so that the crank and rod rotation can dynamically form the proper wedge that "floats" the bushing away from the crankshaft. Or at least that was what I was taught in school. I've never checked it for myself....but the math and forces match up well.
If that is really the way the bottom end oiling works, then 5 psi ought to be plenty of pressure. But although I read about such things, and kind of believe them.....I haven't actually experimented with various bottom end clearance to see if it seems to be true.
Like any old time mechanic/machinist I generally just used plasti-gauge to check my bottom end clearances with a trial dry assembly and if passed then I'm happy. I don't believe I can remember ever having a problem if the plasti-gauge said it was OK.
Anyway, I'll be curious about what the new oil pump shows. I'd kind of expect a new oil pump to show higher pressure at low rpm, but also expect that it wouldn't show as steep a rise as the rpms go up. It will show some pressure rise with rpm of course, but not as radical as an old pump will.
rScotty
