Where is my oil pressure in my fresh rebuilt 351 Windsor?

Question

New oil pump, new bearings, new motor. 85 model w/ edlebrock performer intake and headers. Oil pressure high on initial start up, oil pressure good through 3 gallons of gas worth of fine tuning, took on high rpm test run. Oil pressure was good, backed off accelerator, went 2/10th of a mile, began to accelerate, looked down and oil pressure was dropping. Fell to zero. I shut if off, waited 10 minutes, restarted and oil pressure was high. Continued fine tuning, ran a bit and then pressure fell to zero Again. At which point, thinking it was maybe a malfunctioning gage, held throttle steady 1500 rpm's and I detected a slight rattle. I shut if off, waited 10 min. restarted, and pressure was fine again. Tried to drive, pressure immediately fell to zero, I changed the oil, and 2 x more the same thing happened again. Every restart at 1500 RPM's, oil pressure reading good, try to drive and oil pressure falls. Sitting still at 1500 RPM's every restart, no rattles or knocks. I have 6 quart oil pan with factory oil pump.Hex drive in distributor is fine. Did I blow my new oil pump out or what?

Answer 1

When you put in the six quart pan did you put in a six quart pick up tube?

It sounds like either the oil is not returning to the pan due to a blockage up in the oil galleys or a leak in the pick up tube. I of course am assuming that the oil pan is fulled to seven quarts (six for the pan one for the filter).

My money is on a failure in the pick up tube that is letting it suck air when the oil pan level drops about one or two quarts.

Answer 2

Did you buy a new aftermarket pump from JC whitney or somewhere comperable or did you get one from autozone or other parts house? I ask because i can't tell you how often i've gotten bad parts from parts house everything from starters and alternators both "new" and rebuilt, to power window motors, A/C compressors, all kinds of "bad off the shelf parts" from parts houses. If you got from JC Whitney or Jegs i'd be less concerned about this and lean towards bad oil pressure gauge instead. Something like if it doesn't have at least 40psi to gauge it didn't register at all (i doubt it is gauge due to the rattle you described). A freshly built engine isn't something you want to have oil pressure problems with though it sucks that its happening to you.

Answer 3

Excpt for the rattle, I'd say check the oil pump. Install a pressure gauge in place of the pressure sender and verify the pressure. Maybe the connection to the oil pressure sender is shorted. I still worry about the rattle.

Answer 4

Weird problem - my guess? The relief valve in the pump is malfunctioning.