383 Rebuild Oil Pressure

[Shredder]

Based on the symptoms described, this could be it.

Brand new pump though. Would it be weak already?

 

[Daves69]

Brand new pump though. Would it be weak already?

Unlikely.

Any evidence of the oil aerating?

Let's see, changed pumps, filters, oil, something internal I'm thinking. Some possible, plugged pickup screen, cracked thread on pickup, lifter clearance in bore or wrong for application, loose rocker shaft, bearing clearance?

 

[Heimedw]

I agree with Dave. I would try another new oil pump just to rule it out (good chance it's not the problem) then it has to be internal and like Dave said the list is long that could cause low pressure. Cam bearings not lined up properly, debris in oil passages ext ext. one thing you could try is pulling the valave covers, intake and valley pan and manually prime the system and see if you can visually see a problem? Long shot but if it's something with lifters or push rods you might see it not getting enough oil to the rockers?

 

[69a100]

The only other reason I can think of is, is that your bearing clearance's are off/sloppy causing a slight loss in oil pressure. Other then that, IDK? Good Luck

 

[69B7RR]

Probably a long shot, but I’ve heard of, and once seen the rocker shafts put in backwards after a rebuild or cam swap. The oil holes, instead of facing down into the rocker, were inadvertently placed face up causing oil to shoot up into the valve cover....possibly causing a drop in pressure.....Jim

 

[miller]

The list for low oil pressure is long, and well known. Too many things can cause it.
New 'hi pressure' oil pump? Think I read that right. And only getting 30lbs? Just me, yeah, I'd be looking at the spring, and the valve, and the valve seat. Could easily be a piece of trash, or a burr, letting the valve leak, and giving you low pressure. Even if the spring is top notch!

 

[khryslerkid]

The list for low oil pressure is long, and well known. Too many things can cause it.
New 'hi pressure' oil pump? Think I read that right. And only getting 30lbs? Just me, yeah, I'd be looking at the spring, and the valve, and the valve seat. Could easily be a piece of trash, or a burr, letting the valve leak, and giving you low pressure. Even if the spring is top notch!

This^^^

You can remove the pressure valve from the outsude of the pump without removing the pump itself.

 

[BSB67]

Unlikely.

Any evidence of the oil aerating?

Let's see, changed pumps, filters, oil, something internal I'm thinking. Some possible, plugged pickup screen, cracked thread on pickup, lifter clearance in bore or wrong for application, loose rocker shaft, bearing clearance?

I don't think he changed the pump since the potential problem showed up. So the idea is that there could be a manufacturers problem in the new pump's relief system.

The reason I'm leaning away from motor is that all of those things usually result in near zero pressure at idle.

As mentioned, pull the relief spring, and valve. Inspect, clean and reinstall. If you don't know what those parts are suppose to look like, take a picture and post them as they are arranged upon removal.

Also, when you checked the pressure, how did you do that? Did you use a mechanical gauge? If not, you need to do that.

 

[Daves69]

I don't think he changed the pump since the potential problem showed up...……...

Sorry, I guess I misunderstood post #9.

.

 

[Shredder]

I don't think he changed the pump since the potential problem showed up. So the idea is that there could be a manufacturers problem in the new pump's relief system.

The reason I'm leaning away from motor is that all of those things usually result in near zero pressure at idle.

As mentioned, pull the relief spring, and valve. Inspect, clean and reinstall. If you don't know what those parts are suppose to look like, take a picture and post them as they are arranged upon removal.

Also, when you checked the pressure, how did you do that? Did you use a mechanical gauge? If not, you need to do that.

I replaced the pump since the problem showed up. Pressure was checked with a mechanical pump. Checked the relief spring and valve and reassembled this afternoon. Problem is gone. Idle pressure is around 20 and goes up from there when running. Thank you everyone for the help!

 

[Billccm]

Glad it was an easy fix. Thanks for the update.

 

[BSB67]

Sorry, I guess I misunderstood post #9.

.

My mistake.

 

[miller]

Idle pressure is around 20 and goes up from there when running.

Is that with the motor cold, or at temp? You could have clearances too big, internally, that lowers oil pressure.

Just for comparison, 440 I built, using the stock oil pump, cold start pressure goes to 50lbs.. Warmed up, drops to 30lbs. And I consider my pressure too low, because of the spring. Can't just pull it, on mine...dang motor mount blocks it.

 

[dvw]

Additional info from my experience. Loose bearings do little to effect pressure. Loose lifter bores on flat tappet cams have a bigger effect. Cam bearings rotated wrong would decrease upper end oil with the stock oiling system. Use a weight oil based on oil temperature. I'd bet way to many run 20w50. Dont be afraid of 15 psi at idle. I would recomend close to 10 psi/1000 rpm if it gets beat on. My drag motor survives 7200 using 5w25 JR1 with .003" bearing clearance, bushed lifter bores ar .0025". Pushrod oiled with 16 x .055" feeds. Even then idle pressure is 60psi, 7000, 70psi. The relief spring is cut short enough that the relief valve rattles in the pump.
Doug

 

[moper]

Always always always disassemble the new oil pumps completely and clean them, and reassemble. Otherwise you're asking for problems.