Recently converted my 51 to 12 volt. Installed new gages with new sending units. I now show low or no oil pressure. With the old gages the oil pressure was low (10lbs.). I removed the oil line going to the filter and screwed in a different gage with the same results.
The engine does not knock or rattle.
I removed the oil pan (pan was very clean) and installed a new oil pump with the same results (10psi or less).
Removed drain plug and checked on oil pickup clearance. Pickup is about 1 inch from bottom of oil pan.
Have tried different types of oil. 10w30 and straight 20w and 30w. Still no pressure.
I checked the web site you mentioned and will force oil down the oil sending line into the pump, then try it again.
Forced oil into the line going from the block to the oil pressure sender and filter. Hooked line to guage and low and behold 50 lbs of pressure. Removed mechanical guage and hooked line into sending unit and filter and it shows 40 psi..
Thanks for the web site info '51 ford fan'.
Now i have an extra oil pump if anyone is looking for one. It still floors me when i think that forcing oil the wrong way took care of the problem. I evan took the line off from the guage and ran the engine with the oil running into a cup. You would think that that alone would let get the oil flowing.
Once again thanks for the hand "51 ford fan".