Really baffled and thought I would check and see if member (s) have any suggestions, or diagnoses::

Have a 68 Ford 302 installed in 65 F100 about 8 yrs. ago and the engine has been running fine. I purchased the truck in 72 and never had to tow. Returning home a couple days ago and noticed an immediate drop in oil pressure from 45psi to about 20psi, then it would fluctuate between 10--30 psi, meanwhile, the engine had a tendency to stall and while chugging along and I found it difficult keeping up rpm; in addition, what sounded like metal to metal as if a gear was meshing?? The temp. guage read a steady 180 degree's which is normal.

Unfortunately, started tearing into it before having knowledgable mechanic listen to the engine for possible diagnoses??

*Pulled the distributor and the gear looks fine and turns with no problem.
*Drained the oil and did not find any shavings
*Pulled the pan and no metal particles/shavings
*Pulled the valve covers and rotated engine by hand and valve trane appears to be working fine, turns smothly.
*Checked timing mark location and it's fine
*Hooked up battery and turned the engine small increments at a time and seem to turn easily with no meshing or sound of metal to metal?
*Thinking possible problem with oil pump, or drive gear, used a cordless drill and priming tool the oil pump and shaft spun with out any meshing; however, I had dropped the pan by this time.

At a lose, may be mistaken but would seem with the drop in oil pressure and what sounded like gear slipping/ or messing I could eliminate electrical, or carburation??

Although, using the priming tool it does not appear the problem would be with oil pump or drive gear I am thinking my next step should be to remove and inspect while the pan is off?? If okay thought it best to pull the intake manifold, look for any obvious problem then install the pan, add oil and using priming tool check oil passages for proper flow??

Water pump bearing has been making noise and intend replacing while I am at it and wondered if there's anything I should remove, or check for since this far along??

Trying to describe and diagnose an engine is a problem, reminds me of a trans commercial where customers are attempting to describe a problem they are experience with the transmission by making sounds and expect the mechanic to make a diagnoses?? Anyhow, thought I would check if any members have had simular experience? Suggestions, comments appreciated!!

 

1st, get a portable mechanical gauge & check the oil pressure...if its within spec, its the sending unit or gauge.