Definitely call them. You can get a bad pump out of the box too. A really good shop would check the clearances on the vanes in the pump. The pressure bypass could be bad too.
Some of the old school guys like to put in loose bearings on a race motor. It really shouldn't be done on a street vehicle. Hopefully they didn't do that.

 

The pump drive is a hexagonal shaft that goes from the pump up into the bottom of the distibutor shaft. Small blocks have had problems with these, in my case, stripping on the top end where they fit into the distributor shaft, like a socket. I had a '67 Mustang do that, and it progressed from low oil pressure at idle, to no oil pressure any time. I figured back then I needed a pump, and I was told it was most likely the bearing clearances causing it, but when I took the stuff apart, I noticed the top of the pump drive shaft was completely round. In a magazine, probably the old super ford or something, I saw a pic where the shaft had snapped in 2 from the resistance of the pump, or perhaps something that got into the pump. Any time I have oil pressure issues, I tend to look at this as soon as I eliminate a bad gauge. And whenever I put a new pump in I go to the speed shop and get a Heavy duty pump drive. So far so good.

 

Oh, and let's not forget High Volume oil pumps. If you want to get a little more mileage out of your present engine instead of springing for a rebuild, the high volume or high volume/highpressure pumps are a much cheaper option.

 

Thanks for explaining it to me Mustang. At warm idle I have between 0 and 5 psi, at 2000 rpm I have around 20 psi. When the tranny shifts to 3rd the rpms drop to around 1200, oil pressure drops to between 0 and 10 psi. When I stop it drops on down to where the needle almost touches the pin. So it sounds like the mains are almost worn out if I understand right. Looks like I need to be looking for another engine.

 

Looser clearances are ment for higher rpm operation...if the engine has those types of bearings, than a high volume pump is necessary and is typically used with a larger capacity oil pan. It would be ok to run those on a street motor with the proper pump...but if it's not a high rpm screamer and is a normal rebuild than it's not the proper bearings.

If you were told it was likely to be the bearings than they're wrong and they were. Heavy duty pump driveshafts are strongly recommended by most in any application. It's simply cheap insurance. There is a lot of load on it.



Won't make much difference. You don't want a high pressure pump...and a high volume pump would help...but is it really worth all that work in changing the pan/pump in the truck for it to last a little longer?

To some, maybe...but to most probably not. Either way, you're bearings are worn out and if you let it go too long and they fail...or the metal filings get into other parts...you're just going to have more issues and more parts to replace in the rebuild process. I'd just run a thicker grade oil to get the pressure up a little more to by myself a little more time if I needed it...but it's best to fix it before it grenades on ya or other issues come up.

You should have more pressure than that while driving around. I get about 35psi at 2000 rpm on my 180k 351 that gets 20psi at idle and 60psi at cold start. Goes up to 45 psi when I move it up to 3-4k rpm. And the oil pressure is very linked to the RPM...it's like a mini rpm gauge. I have more than enough pressure and that is how it should be.

When the bearings are at fault and no other issue is there...like the pump and pickup are functioning properly and there are no blockages in the system...than you will see distinct patterns in the oil pressure readings that suggest it's the bearings. When I'm running 1200 rpm, I'm getting about 25-30psi. If you're seeing anything less than 10psi per 1000 rpm...than you need to shut it down or change RPM and make sure you maintain that spec. Anything less, and you're damaging the bearings. 0 psi or less than spec will chew up those bearings in a real hurry. There is some give in the spec, so it's not concrete but it's a safe spec. If you have 10psi per 1000 rpm you know you have enough lubrication but on a healthy motor you should have more than necessary.

I'm not convinced you have simple bearing issues...make sure the gauge is working properly and that it has fresh oil and filter (i think we mentioned that) and if that doesn't work, I'd look at replacing the pump/pickup. If you've run it a lot w/o the proper pressure...you may be looking at a rebuild anyway. How many miles on this motor? has it ever been touched internally that you know of?

You may want to start by renting or getting an oil pump primer, putting it in a drill, and spinning the pump to check and see if you get good pressure before you open anything up.


FYI, for a good home mechanic pulling and installing an engine in these trucks is a piece of cake. I've pulled and installed these about 5-6 times. I can pull a motor in about 8 hours without hustling. I got lucky, the $800 beater truck I bought had a great 351 in it and even though it has 180k miles it's real strong and is in good shape. It is always an option to throw in another used engine to get you by until you rebuild the old one...or just put another engine in it and drive it. A good used 351 is about $400, and if you can verify 140-150psi compression and verify 20psi oil pressure than you can safely know that the engine your buying will last a long time.