390 oiling - pressure reading

[faxon7]

I got a 390 motor that was just broken in, and i got a new oil pump with original shaft and pickup.

After getting around 100 miles on it now, the oil pressure dropped off considerably by the original electric gauge.

So I have installed a mechanical gauge, and right after starting up, it goes up around 30psi, then will drop off again and fluctuate from zero to 10 or 15psi. I've noticed some air in the gauge tube, don't know if it should be full of oil. I've also cranked the motor with valve covers off, and it is oiling up to the valves.

Could the distributor shaft lost contact with the oil pump drive shaft? Or is there some other checks I need to try before tearing off the oil pan?

Thanks again

Josh

[m-mman]

No, if the shaft is turning the pump it will it WILL move oil. If the shaft is broken it should not pump at all. The flucuations are strange

There is always the POSSIBILITY that the hex edges were worn and it is slipping in the pump hole, but I have never actually heard of that happening. They generally either work or they dont.

While pulling oil pans on a truck is not as hard as a car the pump shaft shuld be removeable from the distributor hole with a good magnet for inspection. (as long as you did not put the spring retaining washer on the shaft) Checkign hte bottom of the distributor for wear would be good too.

The other thing to check is the pressure relief on the pump. (a spring against a seat) IF there is crud under the seat or the spring is weak it might cause a strong pump / weak pump condition.

Wierd!

[70_F100]

Since it is newly rebuilt, with only 100 miles and it lost oil pressure, there's a good possibility you're about to lose an engine.

Check everything VERY carefully before running it any longer; mains, rods, cam bearings, oil pump, etc.

[averagef250]

Check the plugs in the ends of the rocker shafts.

FE's need oil restrictors in the heads to have a long happy life. You should not see much oil flow from the rockers at idle with a stock pump.

[fordman]

i have always read that the top end get more oil than the bottom end on a stock motor. when you put a higher pressure pump in you then should put int restrictors to kep the oil in the bottom end because the top end is easyier to get oil up to. well thats what i read anyway.

[faxon7]

Thanks for suggestions so soon. I think I found what is happening.
Evidently I'm losing oil somewhere and the level got low. However, no noticeable drips at first glance.
So I'll be on the hunt for where it's leaking and probably replacing gaskets.
I was looking for a project when buying the truck, and that is what I got!