Weird oil pressure/oil filter problem

440 engine oil pump loses its prime when it sits even for a couple hours and takes 1-2 seconds for it to build pressure, once it builds pressure it is fine and never waivers one bit. I have a mechanical gauge and an idiot light and they both go off at the same exact time. When I take off the filter it is empty and I have put 2 new wix filters and one amsoil filter on with anti-siphon flaps and they all do the exact same thing. At first I thought it was the oil pump and replaced it with a new melling high pressure pump which is what I have had on it for the last 30 years and never had a problem. My valve covers have breathers on them so I don't think its like a vacuum situation drawing the oil out. Is it possible the new filters can't handle the presssure? or is there a better filter?. This is very puzzling to say the least as it came out of the blue this year and this engine has about 25K on it 30 years off use. Any thought would be appreciated. Thanks, Lou

this is why i don't and won't use wix, or k&n filters. the internet hypes them and the sheep follow.

ok, so what do you use?

be opened minded and test some different filters and you'll figure it out.

The Moroso racing filter is a good one. I had the same problem using Milodon oil pump. The O ring on the oil pump snout that goes into the block seemed to be leaking. Every time i changed oil and filter i lost prime. Its the only place i could figure it might suck air. I put a little rtv on the O ring and slid it back up in there. Dont use alot of rtv, because a clump of that could get in the pump and lock it up. You could also try a bigger O ring if you can get it to fit.

One word. Accusump...with an electric valve.

I won't have a wet sump race or performance deal without one.

Have you thought of where your oil pressure gauges are hook up to on the rear of the block and the distance (length of the oil galleys) it is to the oil pump and oil filter? If not stop now and think about how long it is taking the oil pump to fill the oil galleys back up after sitting even for a short amount of time
In my opinion 1 to 2 seconds is good, as long as you don't rev it to the moon on every start up
On draining the oil filter, the oil in the pickup will always drain back into the pan once the motor is shut off, it may suck some of the oil out of the filter, maybe not
ITHs

I've had good luck with the Wix racing filters. I have definitely noticed the issue you're describing with Frams though.

Only use Jomar 100% No Bypass filters on my Mopars, and will even run 2 of them on my 1200hp LS with a remote dual filter oil set-up.

i see....one of those guys.

i'm moparts conditioned.

My pickup tube had a crack in it when this happened to me.

What's strange is it came out of the blue after 30 years. This is an all street car and not really abused so I don't know how the pickup could crack but never say never

No external pickup hose? This should not be happening, with any half decent filter. Try a NAPA Gold.

Once you've tried a few filters and nothing changes, then we have to consider it's internal.

what's the thought on those aluminum case, cleanable, [i forget the name, but they aren't cheap] filters ?

System One. Only thing I use on race engines. Not sure I would use it on a street engine. Maybe with limited miles and short change intervals.

They make different micron rated elements. Maybe with a 35-45 micron element and 10w30. Micron = .001 millimeter. Very small.

Good info.

System One. that's it CM. thanks.
i have one of those i was planning to use, and my car will be one of those limited use, short mile, short change deals, so i should be ok using it.

what i wonder about those alum-cleanable filters is do they have a good anti-drain back and what micron is the screen? something that can be done to check whether it's filter drain back, or some mechanical issue is to simply try a different brand of filter. i don't like wix, k&n, mobil one, and sadly baldwins. i'd find one of the red purolators and try it. they're inexpensive and would make a good first step test. if you notice a positive step in the right direction then try some other different brands. you might be surprised at what you find.

These days, as with everything else, you can't trust name brands.

Wix has repackaged Baldwin, Mann-Hummel, and maybe some others and sold them as their own due to production issues. And trusted name brands are beginning to show up with off shore/Chinese/3rd world/south of the Rio Grande made product. Examine the package and the part for these issues.

I believe Wix Racing (R) filters can still be trusted, but I haven't looked at one in awhile. I know some guys who use the race filters with the external filtermag tool. They are expensive, but they work great at pulling ferrous metal out of the oil.

They have an anti-drainback valve in the end cap.

Plenty of filter info, but again...if the OP tries a number of filters without affecting his issue, he probably needs to look internally.

Filter debates aside the cast iron pump housing of the big block and the internal passages of the block really benefit from enlarging and chamfering the right angle turns to and from the filter.

If you think about the route from the pick up in the sump to the pump itself there is obviously drainback to consider and as the filter is horizontal there will always be a "heel" of oil in the pump regardless of a bypass/anti drainback whenever the engine is not running. Statically the level in the pick-up tube will be the same as the level in the sump with some residual oil in the low spots of the housing inlet.