What oil pressure is "normal"?

[MJRemi]

Thanks for the HF tip. There's one about 2 miles from my house.

[1987Comanche]

I've logged probably a million miles on just these engines, and I have never (that's NEVER) seen one that followed that "10 psi per 1000 RPM" rule.

 

For better or worse mine does :) Cold idle is 40-45 psi, running at operating temp on the highway she has 20-25psi at 2K RPM. Hot idle is just under 10PSI @ 700 RPM. I verified it with a mechanical gauge. Been like that since the day I bought her...I was originally worried about it but 13K miles later I just keep the oil clean and try not to rev her too high :dunno:

[comanche12]

I've logged probably a million miles on just these engines, and I have never (that's NEVER) seen one that followed that "10 psi per 1000 RPM" rule.

 

For better or worse mine does :) Cold idle is 40-45 psi, running at operating temp on the highway she has 20-25psi at 2K RPM. Hot idle is just under 10PSI @ 700 RPM. I verified it with a mechanical gauge. Been like that since the day I bought her...I was originally worried about it but 13K miles later I just keep the oil clean and try not to rev her too high :dunno:

 

thats pretty low to me. :dunno: wore out bearing would cause low pressure?

[Old man with MJ]

My oil pressure gauge is pegged over also,comes down some,I thought it might be caused by not changing oil at regular interval,just add when low.Will try testing sender with an ohmmeter when it warms up some.Where on the engine do you tap in for line for the mechanical gauge,would be more accurate correct?

[Eagle]

Where on the engine do you tap in for line for the mechanical gauge,would be more accurate correct?

I think most people just replace the stock sender with the tube for the mechanical gauge. If you want to retain the factory gauge too, add a short piece of brass pipe and a tee fitting.

[1987Comanche]

thats pretty low to me. :dunno: wore out bearing would cause low pressure?

 

When I did the RMS the lower 1/2 of that bearing looked ok. I figured that I'd find a set of toasted bearings but they weren't all that bad (few very light scratches, plenty of material, no excessive wear). The truck didn't have a full cluster until I installed one so I think it's been like that for a long, long time. Would a leaky head gasket conceivably cause low(er) oil pressure? My truck could be nicknamed the Exxon Valdez :) but there's no oil in the coolant and vice versa. I have the common early 4.0 oil leak on the pass side of the head.

It may simply be a case of my truck having been assembled on a Friday. I found some garbage under the rubber floor mat when I pulled it out.