Big Bart wrote:
Some thoughts
1) Most report only having 10-20 psi at idle. Your gauge may be a little off, (I agree, this gauge is just your typical cheap auto parts store buy) or you have great pressure at idle. My point being watch for oil say at 1,600 rpm when your pressure is say +30psi. No oil then definitely look for plugged push rods. (I saw your typical sludge on the surface next to the rockers from previous owners not changing oil regularly or using certain brands of oil. Back in '78 I had an IHC truck with a 345 V8 and used to use quacker state oil, changed valve cover gaskets and saw all kinds of sludge underneath. Started to use Kendall oil and if I remember correctly in about a years time it was gone. Point being I think you're right, that there could definitely be sludge in the tubes. And if there is sludge in the tubes it very well may be in other places in the oil passages. Like clogged arteries.
2) TNBrett or IDIBranco perhaps can share how the oil runs through the engine. (I have not needed to rebuild mine yet.). It could be the front of the engine supplies oil to the lifters or the back supplies oil to the lifters. So those that are closest have oil pressure, those that are farthest perhaps have little to none at idle. As the pressure is bleeding off as it goes down the valley of lifters. Thans for the oil passage schematic. That helps me out alot. I have read where the "piston cooling jets" have fallen out of the 7.3's or 6.9's and dropped in the oil pan, at least for the ones where the jets were brazed in. I am not sure if that was isolated to IDI's or Powerstrokes.
3) These trucks are more about oil volume delivered than the pressure. This statement is what opened my eyes, this is the same as a pool filtering system, i.e. designed for volume and low pressure. If you restrict any point in the flow schematic it should increase pressure in front of it. Now if the whole of oil passages have accumulated sludge on the walls, all passages collectively will, or theoretically, show increased oil pressure at the gauge. So, if I design an oil passage system with a certain diameter passage and measure pressure at certain RPM's with a known fixed flow, (given the principles of hydraulics) it would follow that to decrease the diameter would increase the pressure using the same flow rates. So if this engine has sludge everywhere, it is everywhere. And that begs the question: short of pulling engine, performing complete tear down and boiling down the block, is there a safe way to dissolve this sludge ( assuming this is correct about the sludge buildup) without large portions of it loosening and clogging the opening to where a oil passage would feed a bearing?
I had saved a lot of these pictures that were posted showing the specs of this engine but have to dig them out. Would you have one handy to post showing the spec values? I am going to pull the rocker arm off and push a clean SMAW welding rod down the tube to see if there is a buildup of sludge and will have to re-torque the rocker back on. Using a clean welding rod is how I cleaned the water passages that had buildup in the oil cooler 4 and half years ago, worked good too.