Oil pressure question Please HELP

[Kern Dog]

I agree. If you're out hammering an engine with only 3 quarts of oil moving around then...yeah, you may encounter a dry pan.
Pontiac Fiero models with the Iron Duke 4 cylinder were fitted with a 3 quart oil pan. These engines were known to overheat and catch fire because of that. Owners may be out and about.....the engine uses a bit of oil and the owner doesn't know, the oil level drops to a point where even under normal operation, there just isn't enough oil to lubricate and cool even a small 4 cylinder engine and....BOOM.

 

[turbine68rt]

"Suck the oil pan dry"...,.
The double edge sword of these forums is and will always be that there are bits of great advice sprinkled among stupid responses.

Flawed opinions like that are on par with the "Manifolds are just as good as headers" argument.

Been running a Melling hv pump for 3k miles since the rebuild using a 402 pan and have yet to lose any oil pressure. Level is always checked prior to any drives, and is always at, or slightly above full.

 

[Loulang]

There is a lot more that can be causing low oil pressure. How fresh is this engine?

I don’t know anything about what has been done to the motor, I took the valve covers off and it was super clean, no sludge at all just nice clean oil. Heads look like they have been done.

 

[Kern Dog]

Been running a Melling hv pump for 3k miles since the rebuild using a 402 pan and have yet to lose any oil pressure. Level is always checked prior to any drives, and is always at, or slightly above full.

The only time that I have ever seen oil pressure drop off with increased rpm was when the oil level was low.
Old engine, fresh engine...same result.

 

[Crowbar]

Running a straight weight oil will increase your pressure as well RC

 

[dvw]

First why is the pressure 25psi? inaccurate gauge? bearing wear? lifter bore wear, restricted filter? thinned oil? weak relief spring in the pump, cracked oil pick-up? Since the engine is assembled, what can we check? First off, find a known mechanical gauge and test. I know both of yours read similar. Verify that the oil pressure is actually this low. If it has fresh oil 10w40 you should be plenty good. What type of filter? Some have shown to restrict flow. If those 2 easy quick steps don't fix it? Then I'd check the pump relief valve and spring. If the valve moves freely, shim or add the high pressure spring. If you've been driving it for a while with no issue you may not even have an issue with the motor itself. Think simple first. Report back and let me know.
Doug

 

[Loulang]

First why is the pressure 25psi? inaccurate gauge? bearing wear? lifter bore wear, restricted filter? thinned oil? weak relief spring in the pump, cracked oil pick-up? Since the engine is assembled, what can we check? First off, find a known mechanical gauge and test. I know both of yours read similar. Verify that the oil pressure is actually this low. If it has fresh oil 10w40 you should be plenty good. What type of filter? Some have shown to restrict flow. If those 2 easy quick steps don't fix it? Then I'd check the pump relief valve and spring. If the valve moves freely, shim or add the high pressure spring. If you've been driving it for a while with no issue you may not even have an issue with the motor itself. Think simple first. Report back and let me know.
Doug

I do have a leak coming from the back of the motor and it’s not the sensor or valve covers, I’m gonna have to drop the tranny and see. This is my first Chrysler 383 so I’m learning as I go with help from everyone. I appreciate all the thoughts and will update as I move forward. Supposed to be getting 2 1/2 feet of snow from now till Christmas so I will be busy taking care of snow removal. I am gonna do the washer thing that was suggested and worked for him.

 

[Kern Dog]

First why is the pressure 25psi? inaccurate gauge? bearing wear? lifter bore wear, restricted filter? thinned oil? weak relief spring in the pump, cracked oil pick-up? Since the engine is assembled, what can we check? First off, find a known mechanical gauge and test. I know both of yours read similar. Verify that the oil pressure is actually this low. If it has fresh oil 10w40 you should be plenty good. What type of filter? Some have shown to restrict flow. If those 2 easy quick steps don't fix it? Then I'd check the pump relief valve and spring. If the valve moves freely, shim or add the high pressure spring. If you've been driving it for a while with no issue you may not even have an issue with the motor itself. Think simple first. Report back and let me know.
Doug

My freshly rebuilt 440/495 has bearing clearances on the tight side. This time I used a standard volume oil pump under the assumption that the high volume pump wasn't needed and that it takes more HP to turn. I've since found that both types of pumps consume similar amounts of HP.
My cold pressure with HV pumps was always 70-80 psi with warm idling pressures over 40. This standard pump gave me cold idle at 50 and warm idling around 20. The quick fix was the black spring from my old pump. With zero other changes, the cold pressure was up to 75-80 and the warm idling pressures were in the low to mid 30s, sometimes dipping to 25.
This is a fresh engine.
The lower pressures may be just fine but if you're used to seeing higher numbers, the lower numbers make you feel a bit worried.

 

[Loulang]

My freshly rebuilt 440/495 has bearing clearances on the tight side. This time I used a standard volume oil pump under the assumption that the high volume pump wasn't needed and that it takes more HP to turn. I've since found that both types of pumps consume similar amounts of HP.
My cold pressure with HV pumps was always 70-80 psi with warm idling pressures over 40. This standard pump gave me cold idle at 50 and warm idling around 20. The quick fix was the black spring from my old pump. With zero other changes, the cold pressure was up to 75-80 and the warm idling pressures were in the low to mid 30s, sometimes dipping to 25.
This is a fresh engine.
The lower pressures may be just fine but if you're used to seeing higher numbers, the lower numbers make you feel a bit worried.

I’m only used to seeing higher numbers in other vehicles I’ve had (modern) this is my first classic

 

[Geoff 2]

Look at this way:

The oil pump/engine is still running 56 yrs after it was built. Why use a different pump?

 

[RemCharger]

Look at this way:

The oil pump/engine is still running 56 yrs after it was built. Why use a different pump?

Good question. So which pump is on the OP'S motor.

 

[Loulang]

There is a lot more that can be causing low oil pressure. How fresh is this engine?

I don’t know anything about the motor I was told it was rebuilt not long before the guy got it and so was the trans you can tell it has been rebuilt and I took the valve covers off and it is really clean

 

[Loulang]

Is there a video that I can watch to do the washer trick? I’ve never messed with a oil pump. **** this is my first mopar and I really don’t want to mess anything up or have **** flying out when I’m taking apart. Thanks for the advice and patience with my novice mopar knowledge

 

[Cranky]

Is there a video that I can watch to do the washer trick? I’ve never messed with a oil pump. **** this is my first mopar and I really don’t want to mess anything up or have **** flying out when I’m taking apart. Thanks for the advice and patience with my novice mopar knowledge

It's not hard....harder to get the pump off and back on the engine than it is to work on the pump. While the pump is off, I would pull the cap off and pull the rotor out and inspect the rotor internals. Can't remember what weight of oil you are using though. What weight are you using? I quit using 10w30 years ago and use 15w40. Anyways, the internals of the pump will look similar to this. Only Mopars don't use a roll pin as they are pressed together but the drive and the rotor body comes out.

Also, here is another thread on the subject. Big Block Oil Pump Spring Change

 

[Daves69]

Is there a video that I can watch to do the washer trick?

Maybe this helps a bit...........


Page 9 & 10 here can give you an idea how it works.......

https://www.mymopar.com/downloads/mtsc/197.pdf

 

[pnora]

My take is what is the pressure at hot idle? To me anything 15-20 or more is fine. Then in relation to RPM change what is the actual increase. At cruise speed if you are holding 30 psi or better I would leave it alone. Now if in fact it is actually stuck at 25 then that is very odd. Normally if all you can get is 25 reved up you will have next to nothing at idle.

 

[Loulang]

It's not hard....harder to get the pump off and back on the engine than it is to work on the pump. While the pump is off, I would pull the cap off and pull the rotor out and inspect the rotor internals. Can't remember what weight of oil you are using though. What weight are you using? I quit using 10w30 years ago and use 15w40. Anyways, the internals of the pump will look similar to this. Only Mopars don't use a roll pin as they are pressed together but the drive and the rotor body comes out.
View attachment 1431743
Also, here is another thread on the subject. Big Block Oil Pump Spring Change

 

[Loulang]

It's not hard....harder to get the pump off and back on the engine than it is to work on the pump. While the pump is off, I would pull the cap off and pull the rotor out and inspect the rotor internals. Can't remember what weight of oil you are using though. What weight are you using? I quit using 10w30 years ago and use 15w40. Anyways, the internals of the pump will look similar to this. Only Mopars don't use a roll pin as they are pressed together but the drive and the rotor body comes out.
View attachment 1431743
Also, here is another thread on the subject. Big Block Oil Pump Spring Change

I take the distributor and shaft out n use my primer tool and drill to pump oil while I’ve been installing Holley sniper and tank and bunch of other stuff over the winter. She’s cost me a nice lil fortune that’s for sure

 

[Loulang]

My take is what is the pressure at hot idle? To me anything 15-20 or more is fine. Then in relation to RPM change what is the actual increase. At cruise speed if you are holding 30 psi or better I would leave it alone. Now if in fact it is actually stuck at 25 then that is very odd. Normally if all you can get is 25 reved up you will have next to nothing at idle.

It’s around 20 at idle and goes up a lil driving, I just thought it should be more. I’m not familiar with classic MOPAR. My dad built a 66 when I was a child and my dream has been to do one myself and here I am thanks to a wonder wife that’s very understanding and a MOPAR lover herself

 

[pnora]

It’s around 20 at idle and goes up a lil driving, I just thought it should be more. I’m not familiar with classic MOPAR. My dad built a 66 when I was a child and my dream has been to do one myself and here I am thanks to a wonder wife that’s very understanding and a MOPAR lover herself

I like facts. What is a lil? Myself if I was looking for ideas and help I would get the motor good and hot. Record hot pressure. Then record at 1,000, 2,000, 3,000 and 4,000 rpms. Then see what responses you get.