Sounds like I'm kinda in the same boat as yourself. I purchase ahigh mileage 98few weeks ago knowing it need some work. After recently completing a 4-wheel brake job I moved onto diagnosing and fixingthe engine.After installing a mechanicaloil pressure gauge I was shock to see it hadlittle to no pressure. Even after aAFT flush, the pressure was still low. Likeyourself I also have a valve tap. Over the weekend I was trying todecideif I wanted to do a top end rebuild, or pull the motor for a complete rebuild.

The plan is to go back to basic. Do a compression test, whichI suspect should be ok because the engine runs smooth. Next drop the oil pan and remove couple rod and main caps for inspection. If everything looks good, I'll clean as needed and re-install components. Then remove the valve covers for inspection and/or cleaning.

My gut feeling is telling me my inspection is not going to be good and I'll probably will be doing a engine rebuild.

Good luck with yours

 

Mike,
What were the oil pressure reading you got?

 

Before the ATF flush, 10psi
During the ATF flush, 10psi
After 30-40 minutes of idling with the ATF it drop to 5psi then I shut it off.

After thinking about it last night, I'm convinced I'll probably will be doing a engine rebuild.Will not know for sure until I start taking the engine apart. My goal is to re-hab this truck for$1000 in parts.