Hello Moparts Guru's need some advice on where to look first,
I have my freshly rebuilt 440, steel crank,rpm heads crane roller rockers Hyd. FT cam etc. I have full groove mains on it and a HV pump.running 10w30 oil I have 60 psi cold and 40 warm and pressure jumps up off the 40 psi to over 60 psi off idle. Issue is after about 2500 3000 rpm the pressure drops out to 15 20 psi. let off the gas and it jumps back uo to 40 and will go up to 60 psi with some light rpm's under 2500. I've tried 2 new gauges with the same result bled the line no change I tried an extra quart and a quart under,no change.the bearings all checked in .002 I went through the pump before I installed it but it was not new I ran it for years on my old engine even though it has very low miles on it.
any thought to where to look first? pump, pickup or oil ?
engine runs good,not hot,no noise and no metal in the oil.
Thanks!

When you took out a quart of oil did you get swap out the filter too?

no fairly new wix filter you think junk in the filter and the bypass is open?

The only time I've seen anything like this it was the filter or the pick-up had some blockage. From your description it seems like when the demand for flow is needed the flow isn't there. I would change the filter first and go from there.

Gus

Is the oil pan baffled? If not, under acceleration your pickup tube might be getting uncovered as the oil runs to the back of the pan and engine. When you let off of it oil runs back to the sump and the oil pressure recovers.

I'm using the street Hemi pan with a windage trey, same setup I used for the last engine for ten years with no issues.

Take the pump off and remove the bypass plug and valve to see if it is sticking when being moved under pressure by removing the spring and use a small magnet to put in the spring hole in the valve and see if it slides in and out real easy
in the top cover
New motors make metal and all the oil in the motor goes through the pump before it goes through the oil filter, hence the tiny bits of metal possibly making the bypass valve sticky
I've had that happen more than once and others on here also have had that
Good luck, please let us know what you find and what it took to fix it

Good info from Cab. Years ago I put a Hemi 1/2" pick up tube I'm my 440, block was drilled and tapped for the larger tube. I spun bearings in two engines before I discovered this; the pick up tube had a 2 1/2"long hairline crack just above where the bend was for the screen. Only reason I found it was because after the second time I was cleaning the tube in a parts washer, I submerged the tube & screen in the cleaning fluid, lifted it up out and had each end covered by my hands as I shook it back & forth to make sure all the filings were out of the tube and fluid was coming out the side of the tube where the crack was. That F'ing crack cost me two engines. Might be worth looking for.

Yes what cab says and I've seen some postings of filters lately coming apart internally. Sadly WIX aren't what they used to be. Royal Purple, Amsoil better.

I agree! Sounds like the pressure relief valve is doing strange things. Sad thing about Wix...used them for years. Just put a Baldwin on mine this year...so far so good!

OUCH!!!!

fresh filter and oil, no change. Forgot to mention I cut the relief spring down a little. Don't know if that would make a difference since I have 60 psi cold and 40 warm @ idle.I ordered a new pickup and spring. Cheers!

That sets a lower relief pressure for sure.

Agreed but shouldn't cause the issues he's describing.
I'm assuming the gauges the OP is using are mechanical Correct?

Where is the bottom of the pickup tube with respect to the bottom of the oil pan? One should e able to see it with the oil drained

if it's is on the bottom as it should be I might try 2 or even 3 extra qts just to see if it responds. Trying to keep it simple,
To me it sounds as though there is not enough oil to keep the pickup submerged at the higher RPM. That could be:
1. The pickup not being on the floor of the pan,
2. The pickup / tube being cracked near the bottom and being uncovered as the RPM increases and the oil level drops a bit
3. Or a drain back issue to the pan
4. A silly question, any chance the rocker shafts are upside down or leaking out of the ends? That may cause a depletion of oil in the pan as the RPM increases


EDIT: The previously mentioned blockage in the pickup is worth looking at as well as anywhere else in the system
Do keep us posted

What was the reason for that? If anything you should have put a washer in there(behind the spring) to give you more pressure not less.

It was 100 psi cold. something I tried thinking it would save on oil leaks. my oil filter used to seem to always leak a little. So I dropped the pan to inspect and all looked good. pickup is in nice and tight with no obstructions. It was sitting about 3/8" from the bottom of the pan so I adjusted down to 1/8".It's a Summit box type pickup. where would the best distance be for this pickup? I've read all sorts of different answers.

Does that pickup have a narrow steel strap under it like the internal Mildon pickups have to prevent it from bottoming flush against the inside bottom of the oil pan?
If it does not I would remove the drain plug and use a thin stiff wire to try and measure how much clearance it has now, if it is between 1/4 to 1/2 inch max I would run it that way
Is it 1/8-inch lower measured off the bottom oil pan rail on the block or is it 1/8 inch off the bottom of the inside of the oil pan?

1/8 from the bottom of the pan is to close. It will restrict the amount of oil it can pull in. Not to mention pull in any contaminants that may be at the bottom. I like the stock style even if it touches the bottom of the pan it will be able to pull in oil unlike the "box"(flat bottom) pick up.

yeah 1/8" is way to close. going with the new pickup and shooting for 3'8".

AMC used a small plastic button to insure the oil pickup didn't bottom on the floor of the pan. Maybe a 1/4" tall.

re: 100 psi cold at idle

If the issue is not mechanical, then look at the oil 'grade', commonly called weight.
There's a chance that its too thick or too thin for the conditions (temperature, and bearing clearances)
100 psi seems high for slow idle - especially in the summer.