I have a 440 with about 1500 miles on a rebuild.  Up until yesterday it had 30-40psi oil pressure at idle and 60+psi above 2500rpm.  Just recently the gauge has been reading 20psi at idle.  If I run the engine much beyond 2500rpm the pressure gets too low for comfort.  Needless to say I'm not driving it until I figure this out.  Up to now engine ran fine.  There is no power loss and no funny noises.

Do any of you folks have theories/advice?  Here's what I checked so far:

Oil change: No parts, bits or piece were in the oil or filter.  Used oil was not frothy, burnt or sludgy.  
Top end: I can see oil flowing from the lifters/rockers through the oil fill hole in the valve cover.
Gauge: Rechecked wiring.  I have no reason to think anything is wrong here as the other gauges work fine.  The sender is new.  
Equipment: A windage tray is installed. The pickup screen was new with the rebuild, as was the oil pump.
Driving conditions: No heavy acceleration, cornering or braking is involved.  

A good possiblity is a restrictive oil filter, I have personally seen a oil filter [Fram & a Mopar factory filter] cause this exact problem.
This past winter I bought a case of mopar filters for my 360, two of them were so restrictive my oil pressure dropped from a normal of 60 lbs at full throttle to 35 lbs. Like you I was concerned and checked every possible problem. In the end I changed the oil and filter and the problem was solved and I haven't had a problem since, this was over six mths ago.  

Thanks for that thought.  I just changed the filter to a new one of the same brand - didn't help.  I'll pick up a different brand to be sure.  That's a quick and easy idea to check it out.  Thanks for the idea . . .  

my opinion, the more expensive the filter the worse it actually is in being restrictive. if you keep your oil changed and clean, get a low cost filter, increase your pressure and still capture the dirt with no problems. i have always been told the high end filters like Fram  are not actually good. FYI my opinion.  

Hey folks.  Thanks for the advice.  I changed the filter with a different brand.  This made no difference . . .  I ordered an oil pump.  I'll try that and then dig into the motor itself if I have to.  Has anybody ever had a similar issue where the oil pressure drops below 10psi as the RPMs go up, and then the pressure returns at idle?  If so, what was it?

thanks!  

I had a small block with a rod bearing problem were the oil pressure would drop when accelerating.
Good Luck  

It may be something simple like a metal flake got in the pressure sensor.  When you bump up rpm's the flake gets pressed in the sensor perhaps and the pressure reading drops.  Longshot I know but a sensor is pretty cheap to try.  I've always used the mechanical oil sensors and gauges and had good luck.  

This is fault tree isolation lodgic, as each item checks out ok move on to the next before starting the engine.
Check the oil pressure sending unit's port, run some safty wire down it or hit it with shop air. Check the relief valve popet in the oil pump and the spring. Next, check the dist drive gear and see if the hex drive for the oil pump is ok. Take the pump off and disassemble it. Look for any debris and check the clearance, then blow shop air down the oil supply (not pressure) port. Then pull the oil pan and look for any debris that could restrict the oil pick up. Also check the oil pick up and make sure the windage tray has not chafed a small hole in it. Check the oil pump pick up to pan clearance. Next pull each main and rod cap one at a time and check the bearings. Don't fear about disturbing the bearing, we do it all the time on the Alky motor. If it did not spin the first time....

Andy  

Thank you for the advice drmopar, jerryg7 and Andy.  I have a new oil pump and a mechanical gauge coming.  In the meantime I will try some of the physical inspections.  Whatever I find I'll keep y'all posted.  

Hi all - I found it.  The oil pressure was fine - 50psi at idle, 75 at anything above 2000.  My sender couldn't take it.  

My mechanical gauge shows that at low RPMs the pressure pulsates a bit.  I think the pulsation is causing the faulty sender to show 20psi.  At higher RPMs (above 1500) the pulsation stops and the bad sender shows 0psi.

So I rushed into buying an oil pump and a new oil filter.  I won't complain one bit!  

Thanks for all your thoughts and advice!  

Sometimes its better to be lucky than good. I have ran into a ton of problems with small electrical parts this past couple of yrs. If you look most are now made in China.  

Awesome find and I agree it is better to be the sender than anything else!  I agree with the Dr on the chinese parts crap.  I've been to China many times and walked around some of the blocks with a local friend of mine where there are hundreds of vendors selling cheap crap for pennies!  You would not believe the stuff I've seen in Shenzhen (and you can find for example at places like Harbor Freight...)