20 PSI oil pressure

[biomedtechguy]

Just a broad observation that parallels many I have read.
Appx 15-25 psi oil pressure at hot idle, engine at full operation temperature.
Add about 15-25 psi for a stone cold motor at fast idle, like when you first start it, so that's 30-45 psi (I've seen higher psi than that under those conditions with 40, 20/40 and 20/50 weight oil)
My 440 that has unknown hours/miles on it is a stock short block as far as I can tell with 6 pack forged crank and 6 pack rods, stock flat pistons with valve relief notches, and the unique 6 pack offset weighted harmonic balancer.
In South Louisiana, I run Valvoline VR-1 20/50 year round since the "warmer months" which is about 8 out of 12. If VR-1 was available in a 20/40 I'd run that in the colder 4 months, but usually I don't drive it much then anyway.
My oil pressure runs around the numbers stated, around 50+ psi stone cold fast idle, then at full operating temp (185°-195°) at 850-900 RPM idle it drops to about 25 psi and increases to around 60-65 driving around.
If it ever drops below 20 psi I would be concerned.
I installed a mechanical oil pressure gauge in the 65 GTO years ago because the factory gauge sucks and the 421 it turned out had a really bad crank bearing. At full operating temperature, the oil pressure would drop to 5 psi at 800 RPM idle speed, much lower than cold pressure. It was trying to tell me it had a bad bearing. I had a performance oil pump installed when we had it rebuilt, but I am cautious about "high volume" and especially "high pressure" oil pumps. High pressure can be moderated with the bypass pressure spring, but I'd rather get it close than have that spring bypassing too much. Too much pressure and it takes away from the "cushion" that oil provides bearing gaps. Too much volume could tend to drain the pan and push a lot of oil "up top".
Just my opinion and experience. I'm not an engine builder nor expert.

 

[Daves69]

If pressure is always the same with different gauges I'd first suspect the relief or a worn out pump. Internals next. When you pull the filter, you might open it up to see what's in it.
My old 440 doesn't see a lot of run time. Still has 35-45 psi @ 800-1100 rpm. (Lol, ya' it's running on M-T here )

 

[dvw]

If it makes 20 at idle there arent any plugs missing. If the pressure doesnt increase with speed the pump is bypassing. My bet is the spring is weak. Stiffening the spring wont do anything for idle pressure. But it should produce more pressure as the speed of the pump increases. Now if we were talking 5 idle/20 at speed that's a different issue. Sure thicker oil will increase pressure. That's because it reduces flow. The only time you need thicker oil is if your engine runs a higher oil temp. All oils thin with temp. Summer long runs may require thicker than freezing short runs in the Winter.
Doug

 

[Marco]

Hi everybody,

I shimmed the spring yesterday and it indeed raised the pressure (20psi idle, and 30 at about 1500 and up). Everything seemed al right with the spring (pink) not broken or anything.

I just ordered a high pressure spring kit i'll be installing that when it arrives, I hope to get to about 40 psi at highway cruise.

For some reason I did not manage to get the cup where the spring pushes against out, is this normal? I tried moving it with my pinky but not get it out.

I'm not using a fram filter btw hahaha just a mopar performance one.

Gr Marco

 

[joemish]

440 in my Superbird rarely hits 10psi, been that way for over 30 years. Has lots of oil flow and doesn't knock, all that matters.

If you want to see if you can increase the pressure, shim the oil pump bypass spring with a washer or two.

when you hear the knock it will be too late.

 

[69Bee]

FYI, the Mopar high pressure spring kit from a long time ago (more than yesterday), the spring was black, and the pressure was 80psi. If you are going to get around 40 psi, your problem still exists, and should be corrected. You are only putting a band aide on the problem and not correcting the root cause.

 

[dadsbee]

when you hear the knock it will be too late.

31 years since I bought the car... still running and not too worried about that changing anytime soon. If it goes it goes, pretty good mileage out of a 50 year old warranty block..

 

[dart4forte]

Another possibility is you are bleeding oil off the pickup tube. Either loose or there’s a hairline crack. Something to consider.

 

[69Bee]

Another possibility is you are bleeding oil off the pickup tube. Either loose or there’s a hairline crack. Something to consider.

That is the suction side, so it cannot bleed oil, but it can induce air into the system and that could be an issue.

 

[Daves69]

For some reason I did not manage to get the cup where the spring pushes against out, is this normal?......

That's the valve. You may not be able to remove it like that if it's varnished up like lifter bores can get. It needs to be free and should not hang up in either direction. I'd pull it off and check it out.

 

[Marco]

Hi, everybody

Thanks for the responses!
I installed the high pressure spring kit and it did not do anything for me, the cold oil pressure is now about 40 but seems to drop when rpm increases....

Also when hot idle pressure is about 20 but does not move when rpm increases.

I've got full groove mains so my guess is that there is not enough oil flow. I ordered a high volume pump to test this. I'm running 15w40, when im running heavier oil my lifters start ticking so that's a no go.

When installing the high pressure spring I managed to get the plunger out with a magnet.

 

[dart4forte]

That is the suction side, so it cannot bleed oil, but it can induce air into the system and that could be an issue.

suction yes but if you have a crack or a lose pickup oil will bleed out.

 

[Master Gunner]

I've got full groove mains so my guess is that there is not enough oil flow. I ordered a high volume pump to test this. I'm running 15w40, when im running heavier oil my lifters start ticking so that's a no go.

What size oil pan do you have? Reason I ask is a high volume pump can empty a factory pan and have the oil in the "top" of the engine.

Mark

 

[69Bee]

suction yes but if you have a crack or a lose pickup oil will bleed out.

Incorrect, the oil cannot leak when it is at a negative pressure (suction), and the crankcase pressure is approximately 29.9212 in Hg or 14.696 PSI at sea level. It could potentially leak down once the engine has been shot off, but not while running. The formula to calculate the suction pressure is cumbersome for assumptions, so suffice to say that it is going to -3 psi or better (more negative), so it cannot leak oil while running...

 

[Wietse]

What size oil pan do you have? Reason I ask is a high volume pump can empty a factory pan and have the oil in the "top" of the engine.

Mark

Im using the Melling HV pump with a stock oil pan on my 440, never had the oil pressure drop due to starvation of low oil level.
But i always keep the oil level just above the "max" level.
60 psi all day with 20w50 oil.

 

[Wietse]

Marco,

Has the oil pressure been this low since rebuild, or was the pressure higher before?

 

[justcruisin]

I have fully grooved mains, HV pump, standard relief spring, runs 48psi cold, at any rpm, drops to 35psi hot idle, 5w30. The HV pump is good for maintaining pressure at idle with a thinner oil but if all is OK the standard pump should give the same reading at revs with normal bearing clearances. Cold oil pressure at idle with the HV spring was 70psi. I would be dropping the sump and checking the screen for a blockage or a split in the pick up tube or bad seal at the block.

 

[Slap Stick]

If a HV/HP pump was bad Ma wouldn't have used them.

 

[Master Gunner]

True, but the HP engines came with a 5qt pan vs the standard 4qt ( filter holds about 1qt)

Mark

 

[dadsbee]

Sorry, but an HP's 402 pan only holds 4 quarts...