I just rebuilt the engine of my Ford Truck, a 92 with a
351. I took it to a mach-shop and had everything checked.
Bought a master rebuild kit including a reman oil pump.
Assembly was normal; nothing out of normal. We did forget
to plasti-guage the rod bearings. Anyway, installed the
engine; cranked it over with no plugs to insure oil pump
primed. Fired it up with no (major) immediate problems. Oil
pressure was within limits for the dash gauge. As the
engine started to warm up the pressure dropped off to zero
rather quickly. Shut off the engine. Restart would give
initial oil pressure, then zero, accelerating it to 1500
rpm would bring up the pressure. Borrowed a friend's direct
pressure gauge and a new sending unit. hooked it up with a
"T" fitting. Warm oil pressure reading 5 psi, cold and
revved up in the high 20's. Much to low for a rebuild.
Talked to the machine shop today. No work was needed on any
of the journals, so stock bearings were used. He said the
cam is progressively smaller in size so doubtful any
problems there. The crank gauged OK, so were checking the
rod's tomorrow to be sure the wrong bearings weren't given
to us (Something about a 400 bearing fits but is off size
to cause a loss in pressure.) I'm at a loss as how to solve
this problem so I don't have to remove the engine again.
What are the chances of the oil pump being bad? Any
suggestions on how to find the loss of pressure while the
engine is out? Suggestions?

 

There may be a problem with the oil pressure relief valve. If something got stuck in the valve it might cause these symptoms. Try surfing over to the [link:www.melling.com|Melling] web site and read the support bulletins.

 

>
>There may be a problem with the oil pressure relief valve.

That would be my bet also, I've seen it happen
a couple of times, once on a Jag V12, very spendy
rebuild I did for a friend...

Steve & the Rockette
'63 F100
'68 F100
'72 Capri 2L
'73 Capri 2.6L V6
'73 MG B GT 2.6L V6(Ford)
'98 Contour SVT 2.5L V6, That blowed up real good...
'01 ZX2 (No Mods yet)

 

rear crossover plug removed by mach shop not reinstalled. :7 truck on it's way together now
Steve

 

myeverett, Hopes that takes care of your oil pressure problem.

I had the same thing happen to me on my 460 rebuild, the machinist left out a front oil galley plug on mine ( would have been behind the timing chain cam gear had I not caught it ), but fortunately I caught it while I was assembling the engine.

I find it a good thing to even double check the guys that do this stuff everyday.

 

Whew,that's a relief.Once had a friend fixing to drop in an expensive 351 stroker in a 69 stang.We were bolting on the flywheel and I said"where are the rear oil galley plugs"Duh, the machine shop did'nt reinstall them.Talk about an oil leak.

Billy

 

[updated:LAST EDITED ON 19-Nov-02 AT 08:16 AM (EST)]it could be since you did'nt plasti the main bearing they could be to tight so when it warms up and they expand there cutting off oil presure thought the crank.