I have a 5.0 ho out of a mustang in my truck. It was ran dry of oil but was shut off before things were too bad. Well I replaced the oil and it began to build pressure and the dry engine noises went away. Well now the oil pressure will b about normal at idle but as soon as I apply any throttle the pressure falls too 0. Is there and chance at all that this could be a pump issue like maybe the shaft that comes from the distributor is stripped inside the pump or something of that sort or should I just consider it toast? Any help will be greatly appreciated.

 

Likely the main bearings are toast. What you are seeing is the crankshaft moving down away from the upper bearing half and you are gaining too much clearance and your oil pressure goes away because of that.

Try this: stand and watch the balancer as you rev the motor. Likely see it move all around. Not good. Or remove the belt and try wiggling the balancer by hand. You can probably feel the slop. Not good.

Game over.

 

i did the same thing man. its probably toast. you might be able to rebuild it but that would probably require a line hone of the mains, crank polishing and balanced as well as replacing any valve train parts that suffered from the lack o oil.

You are lucky you got it stopped in time. Mine let me know I was out of oil by shooting a connecting rod through the oil pan.

 

Ya see that's the thing. It's till fires right up and idles perfect and smooth it just ain't gettin oil it seems. I'm just gonna have to drop the pan I guess and check out the pump and see if the prob is there. After it did this the original time I got it running again and it was gettin oil and it wasn't makin any noise or anything then the oil pressure started actin up again and it got noisy again bc it stop gettin oil again.

 

Freightrain: thanks! I'll try that as soon as I get home. That what I'm thinkin is goin on. But after the truck did this the initial time I filled it full of 15w 40 and it gained oil pressure and got quiet and I drove it around all yesterday and then it sat for a while and when I started it up to go home it's started this up again out of no where like I said I drove it all day with no issues the motor wasn't tickin or loosin power or nothin. Then it cooled down and I started it again. Then I was back to square one. But I'm counting on it bein the main bearing.

 

Are you still using the factory gauge or do you have a "real" one installed?

 

This same exact thing happened to my 351w..
Thought it was a bad guage, kept driving it.. Then it ceased up on me so beware.

 

When I see an issue developing that concerns oil pressure, the first thing I do is install a manual gauge. I have a large dial, liquid filled gauge just for this. I don't trust the current gauge to be either wrong or right. I always HOPE the gauge took a dump but that's usually a pipe dream!

 

I actually purchased an oil filled manual guage but I'm not sure where to install it on this engine and haven't found a legit answer. It's an '87 5.0 H.O. And I know it's not just the guage bc the engine started to make the "dry engine" noises. Not knockin just dry lifter tick type sound like it did when this initially happend then I filled it full of oil drove it all day and then parked it long enough for it to get cold and started it up and all of a sudden again it isn't gettin oil anymore and started to get loud. I watched the balancer while it was rubbing and didn't seek to b sloppin at all. Once I hook the man guage up and it shows it isn't gettin any pressure at all even at an idle does that lead to the pump? Like I started the engine has no knock and runs smooth. It's just so odd that it did this then ran fine a whole day just like it always did then I start it up and no oil pressure. Thanks y'all.

 

A malfunctioning valve in the oil pump will cause this. And on a rare occasion, a bad oil filter can, too. Swap the filter out and see what happens.
I hook my gauge in the port the sender screws into. I have a grease gun hose on mine so I can place it outside the engine compartment if necessary.