I have a 93 GMC sierra with a 350 engine. I drove it to work a couple of days ago and it ran fine. When i left work i noticed the lifters starting to rattle. I looked down to see if my oil pressure was low, but to my surprise it was over 80 psi. I have changed the filter, checked the filter bypass, and changed the oil sending unit under the distributor. I have also pulled the valve cover on the drivers side and all the lifters are all oiling. I know several things can cause high oil pressure, but the rattling does not make since to me. Any suggestions?

 

You need to install a mechanical gauge and see what the reading is.
The valve train noise and pressure issue might be a coincidence.
If it actually is that high I'd suspect a stuck pressure relief in the oil pump.

 

I had a ford with a 4.9 in it that had super high oil pressure, and it kept blowing oil oil seals all the time. What the problem was is when the engine got rebuilt, the guy used a 93 block, with the 80 head and all that, but left in the 93 rods. the 93 rods are longer then the 1980 rods, and that's what caused my problem.

 

Do you have any updates on your issue?

 

the actual sending unit for the dash is different from the one near the distributor. It is lokated just above the oil filter driver side below the exhaust manifold. Thought I was loosing my mind till I found it. Haha