I just finished a cam and intake swap on my 400. Gave it a new Melling OEM oil pump, and it still lacks strong pressure. She cranks out 50 to 60psi at start-up, but after it gets warm, she drops to 5 to 10psi at idle, and 20 to 25psi cruising. Not really enough to make me feel warm and cuddly inside.

78 f250 4x4
400 auto

 

Possibly worn main and rod bearings, how many miles?

 

Are you using a mechanical gage ?

 

It's a common problem. It is usually caused by too much oil to the lifter galleries. To solve it you should install restrictors in those gallery ports. However that requires nearly complete disassembly of the motor.
You shouldn't be overly concerned about it, because the oil pressure is measured after all the mains have gotten oil. The only part that gets oil after the oil sender is the valve train on the drivers side.

 

the 400 is good for that. i had one with the same problem. mine was cuz the main and rod bearings were shot. it ran for 4 years like that before a rod broke. does it have a tick to it?

 

Instead of pulling it to install restrictior, just run an external line from the front pressure port (behind the P/S pump) to the rear where the oil sender is. You may still have low pressure, which is common in Clevelands but at least you'll know the supply is there for the rear mains.

 

Drop the pan and replace the rod and main bearings with properly fitted bearings. You may have to shim the bearings. Measure carefully and check the results with plasti-gage. Restrictors and oil lines are just band-aid approaches.

 

Regarding an external oil line:

What are the different ways to do that? Expensive looking hose or can just pipe be used?

I'm giving my 400 a quicky rebuild with a new oil pump and timing set and would like to do this little trick to help with the rear main oil problem I hear about.

Any insight would be appreciated. Thanks, Gier-head

 

I ran that line using AN type fittings and a hydraulic hose made up at the local parts house. Been awhile but probably cost me $20-30 altogether.