No oil pressure, Knocking

[LT1XJ]

Occasionally was losing oil pressure while driving. Mainly if acceleration while turning, sometimes just while driving. Checked oil and even added some extra just to see. Pressure usually comes back up, worst case (which happened twice) I shut it off and let it sit and then it was fine. Well, a few days ago it dropped to 0 and started knocking and it never came back. Pulled the pan, no obstructions and I don't see any problems with the pickup. Some slight wear on the filter adapter and some on the top of the filter housing. motor was replaced by PO about 40,000 miles ago. Is a cracked timing cover a possibility? main/cam bearings? Oil pump?
Just looking for ideas If I have to pull the motor I may go a different route. I am just worried about putting 400 into a timing cover,etc. I have one of the nickel ones on the other waggy. I may want to go with a 401 or a 6.0 if I have to pull it.
Thanks for any help,
Dustin

[tufcj]

There should be a small button on the bottom of the pickup. It keeps the pickup from sucking itself to the bottom of the pan. If it's not there (there's a small hole), brazing on a 1/4" nut will work.

The other thing could be a cracked pickup tube allowing the pump to suck air and lose prime.

Wear would cause low pressure, but not a complete loss.

Bob
tufcj

[ironman_gq]

sticking relief valve (big nut with a spring and piston behind it) will cause intermittent no pressure

[northplainsdrifter]

sticking relief valve (big nut with a spring and piston behind it) will cause intermittent no pressure

Can you just unscrew and clean it out? I'm having fluctuating oil pressure. It's start's off at 60 when cold, holds about 40 for a bit, then drops to 20 when hot, sometimes it comes back up.

[tufcj]

Yep. Just unscrew the 7/8" nut, be careful because there's a fair amount of spring tension behind it. Clean the spring, plunger, and passage with brake cleaner. Make sure the plunger moves freely in its bore. The plunger goes in point first.

You could also replace the spring. They do weaken from heat and age. A standard Melling oil pump kit is under $20 at most auto parts stores (it includes a spring and plunger), or you can get the custom upgraded parts here at Bulltear.

Bob
tufcj