Help with low oil pressure

[Ricks72Chlgr440]

My builder said to use 10w/30 but both the idle and higher RPM pressure was too low for me. I moved up to GP-1 15w/40 and that brought the idle pressure up to around 20 and the highway pressure to about 50. I also changed the pressure spring to the black hemi at the same time. Still using the standard (not high volume) pump.

Edit: I had my builder install the 440Source stroker kit for me. They never indicated what the bearing clearance was. For me to have such low pressure the main clearance must be north of .003. If I ever pull the engine I'll know, but for now the pressures are fine for my street driving.

 

[moparmike68]

My builder said to use 10w/30 but both the idle and higher RPM pressure was too low for me. I moved up to GP-1 15w/40 and that brought the idle pressure up to around 20 and the highway pressure to about 50. I also changed the pressure spring to the black hemi at the same time. Still using the standard (not high volume) pump.

Edit: I had my builder install the 440Source stroker kit for me. They never indicated what the bearing clearance was. For me to have such low pressure the main clearance must be north of .003. If I ever pull the engine I'll know, but for now the pressures are fine for my street driving.

Was that 20 psi idle at hot/running temp? Yeah I’m guessing that my bearing tolerances are probably the issue too. Not too sure how good my “builder was”?🫩 as I have no idea what he did or what tolerances were. I didn’t receive any paperwork from him regarding measurements/tolerances etc. He was an older guy and was probably winding down his game and didn’t care much.? My luck. I’ll be more involved next time I have work done! I’m hoping that the straight 40 weight will get me some more pressure.

 

[Ricks72Chlgr440]

Was that 20 psi idle at hot/running temp? Yeah I’m guessing that my bearing tolerances are probably the issue too. Not too sure how good my “builder was”?🫩 as I have no idea what he did or what tolerances were. I didn’t receive any paperwork from him regarding measurements/tolerances etc. He was an older guy and was probably winding down his game and didn’t care much.? My luck. I’ll be more involved next time I have work done! I’m hoping that the straight 40 weight will get me some more pressure.

Yes, 20 hot idle. I'd be concerned about running 40 straight weight oil since it does take awhile to flow when its cold. You don't want to delay getting lube to the engine. The 15w/40 works for me but you could also use 20w/50 if you're really concerned. At least the 15 I use or the 20 would flow oil faster cold than the straight 40!

 

[moparmike68]

Yes, 20 hot idle. I'd be concerned about running 40 straight weight oil since it does take awhile to flow when its cold. You don't want to delay getting lube to the engine. The 15w/40 works for me but you could also use 20w/50 if you're really concerned. At least the 15 I use or the 20 would flow oil faster cold than the straight 40!

I usually only drive the car when it is warmer: spring, summer early fall. I was concerned with the

Yes, 20 hot idle. I'd be concerned about running 40 straight weight oil since it does take awhile to flow when it’s cold. You don't want to delay getting lube to the engine. The 15w/40 works for me but you could also use 20w/50 if you're really concerned. At least the 15 I use or the 20 would flow oil faster cold than the straight 40!

Thanks for your reply. I just did a little more research and you are correct that the straight 40 is thicker at start up than say 0w or 15w. I do drive the car during the fall and there may be some “cold” start ups and the straight 40 would take longer to get to parts of the engine as you said. I don’t like that idea, but 0w and 15w are thinner at beginning, but retain the viscosity at 40 when oil is hot, therefore I think I am going to try the 15w40 instead of the straight 40. And see if my pressure increases.
Thanks again to all of your replies guys!

 

[moparleo]

Lets start with what should be obvious.
Is the oil pressure gauge giving you accurate information ?
Get another manual oil pressure gauge and install in the proper location and test again.
Don't rely on electrical gauges or sending units.
If you want to also have your dash gauge working, just use a "T" fitting for the sending units and plumb both.

A fail safe that Dodge used for years on their Vans was to install a oil pressure switch set for 10 psi and attached to the the Electric fuel pump power wire.
This would kill the pump if the oil pressure dropped below 10 psi.
Saves the engine from bearing damage

If you are replacing an oil dipstick and it is not marked or the tube is not standard length is simple.
Start with the filter removed and the oil pan dry. Starting with no oil.
Install the filter, add the proper amount of oil and start the engine.
Run for a few minutes and shut off.
Check oil level on stick in 10 minutes.
Mark the stick with a notch.
This is now the exact amount of oil that you put in.
Length of the tube or stick doesn't matter as you have just set the level with the exact amount of oil required.

 

[Chryco Psycho]

This could be a few things ,
I have seen some oils run low pressure & that is the easiest to change & see what the result is
I have also seen lifters with the oil groove around the body too low or high & bleed oil past the lifters when sitting low in the bores , this is also relatively easy to check , you could pull a lifter with a magnet & compare to a new lifter or different lifter .
The other possibility is the brg clearances were machined wrong & are too lose , you would have to pull the pan & drop a rod & or main brg to check . easy to test with plastigage .
You could also check to make sure the pick up tube is sealed & tight , if it is loose it could be pulling some air in .
Melling pump are very good & I doubt that is your problem

 

[moparmike68]

Lets start with what should be obvious.
Is the oil pressure gauge giving you accurate information ?
Get another manual oil pressure gauge and install in the proper location and test again.
Don't rely on electrical gauges or sending units.
If you want to also have your dash gauge working, just use a "T" fitting for the sending units and plumb both.

A fail safe that Dodge used for years on their Vans was to install a oil pressure switch set for 10 psi and attached to the the Electric fuel pump power wire.
This would kill the pump if the oil pressure dropped below 10 psi.
Saves the engine from bearing damage

If you are replacing an oil dipstick and it is not marked or the tube is not standard length is simple.
Start with the filter removed and the oil pan dry. Starting with no oil.
Install the filter, add the proper amount of oil and start the engine.
Run for a few minutes and shut off.
Check oil level on stick in 10 minutes.
Mark the stick with a notch.
This is now the exact amount of oil that you put in.
Length of the tube or stick doesn't matter as you have just set the level with the exact amount of oil required.

I have had a manual pressure gauge (with small tubing ) mounted to a fitting on rear of block. I am as I have an electric sending unit screwed into the other threaded port at the rest of the block. I also bought a separate oil pressure gauge set with multiple adapters and I plan to test it and see if it matches the other gauge.
I will check my dip stick markings when I add the oil and new filter.
Thanks

 

[pschlosser]

I have had a manual pressure gauge (with small tubing ) mounted to a fitting on rear of block. I am as I have an electric sending unit screwed into the other threaded port at the rest of the block. I also bought a separate oil pressure gauge set with multiple adapters and I plan to test it and see if it matches the other gauge.
I will check my dip stick markings when I add the oil and new filter.
Thanks

We are all hoping the issue is not poor (bearing) tolerances often associated with a worn engine. But, if your measuring instruments aren't wrong, then there are no false readings and you do seem to have low oil pressure. The question is, why?

A newly rebuilt engine, with less than 1000 miles, would not normally show low oil pressure when hot and at idle. By low, I refer to something below 15 PSI. Even on an engine revved to red-line and broken in running quarter mile trials, would still have strong oil pressure when hot and at idle. By strong, I mean 25 PSI or more.

But we presume some things about the rebuild, that it was done with correct tolerances in all the right places.

You may get lucky, it may be a correctable issue causing the low pressure. But as we rules those out, you're left with pulling the engine and having those tolerances checked.

Do continue confirming you have appropriate oil capacity, and oil flow (via pump) through the engine. But I don't think those, or the oil weight, is going to have a strong influence on the hot-idle low-pressure problem.

You want a solid 25-30 PSI at 700 RPM idle. I am curious how high is the pressure (at idle) when the engine is cold? and how high does it go when the engine is at.... 3000 RPM when cold? Does it go above 40PSI?

And what are those numbers when it's hot? A significant difference in numbers between hot and cold, I believe, points to bearing tolerances.

 

[chargerdon]

three things:
1) changing the spring does zero good for pressure at idle. A stiffer spring simply allows the pump to make more MAX pressure. I e it raised the bypass point which is not your issue.

2) A high volume (NOT HIGH PRESSURE) pump does pump more oil and therefore will raise the pressure even at idle.

3) The idiot light on our vehicles is set to stay off unless the pressure drops below 7 psi... So long as your getting oil to the valvetrains then you probably have enough.

I have a 383HP in my 66 Charger at it experiences the same problem at HOT idle. I.e low pressure, but at highway speeds above 1500 rpm it will be in the 30-45 range. Cold it always shows 65-70 PSI even at idle which is what the cut of spring allows. To counter the problem i installed the High Volume pump and switched to 20-50W oil. With this at full hot it will still show on my mechanical gauge between 5-10 psi and my idiot light never comes on. Realize that in a 66 Charger the oil gauge is a slow reacting gauge so id have to be at idle for about 5 min or longer to even show the idiot light.

My mechanic buddy who knows Mopars said quit looking at it!! Its fine !!

 

[540HemiCuda]

I agree with some of the above posts, but disagree with some of the opinions offered.

The OP's hot oil pressure is too low. He should address it.

If the OP does decide to go into the engine to investigate, he does not necessarily need to pull the engine. IF he decides to go that route, then the very first thing to do would be to pull the pan (that can be done with the engine in the car) and Plastigage the rod bearings. If they are on the wide side, oversize bearings USED to be available which would tighten up the clearances. All that can be done in the car. We have used Plastigage in many applications for decades and have found it to be very accurate as long as it is fresh and soft. I, personally ALWAYS Plastigage the rods as I assemble an engine just to be SURE they are where I want them to be.

But the OP said that he would prefer not to go that route. So, trying heavier weight oil and then, if needed, an HV pump have a very good chance of getting him where he needs to be. Which in my opinion and experience is around 15 pounds hot idle (somewhat depending on his idle speed) and about 60 pounds hot max, preferably by 3,500 or so. None of that is set in stone, just good bench marks to shoot for. Some more would not be a bad thing nor would slightly less. They are just ballparks.

.

 

[Challenger RTA]

electric sending unit screwed into the other threaded port at the rest of the block.

Here again. If the electric sending unit has to much thread sealer. It will not give you the correct reading. Not a good ground. Think simple. KISS

As I remember. A wise man once told me; Find the laziest guy on the job. Have him do the job. He will find the easiest way to get it done.

 

[moparmike68]

Here again. If the electric sending unit has to much thread sealer. It will not give you the correct reading. Not a good ground. Think simple. KISS

As I remember. A wise man once told me; Find the laziest guy on the job. Have him do the job. He will find the easiest way to get it done.

Thanks, I’ll check that. I didn’t really think about it needing to be grounded. I also have a manual gauge installed on the other port next to where the electric sender is.

 

[Challenger RTA]

Thanks, I’ll check that. I didn’t really think about it needing to be grounded. I also have a manual gauge installed on the other port next to where the electric sender is.

There are a some good members here that are knowable. But their not there looking at it first hand. Their just giving their 2¢ as I am. Their are some videos that I came across. I'm not an expert. The videos explain a lot from what I understand.
It puts things in prospective. At least for me.

Thread 'Science Friction: Squeezing the snake out of the oil!'

Feb 2, 2026

Break in oil. short and simple.

Do Classic Cars (1951-1996) Actually NEED Special Oil?

NOTE: This video is NOT about flat tappet camshaft break-in or racing engines. Please refer to this video about cam break-in. https://youtu.be/Fj2NSteaPnM?si...

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Good analogy of paint thickness.





Rubber bands stretch and break

LAB RESULTS: Pennzoil Ultra Platinum vs Mobil 1's NEW Formula

There are three different formulas of 0W-40 Mobil 1, and one of them is a brand NEW formula. How do they compare to Pennzoil Ultra Platinum 0W-40?Let's take ...

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• Challenger RTA
• Replies: 3
• Forum: Mopar General Discussions

 

[Challenger RTA]

This is what I would do before I take anything apart.

Treat it like a rebuild engine. Prime the engine.
I would check to see if the oil pump is working.
Pull the distributor and spin the pump to see if you have oil. It's a good tattle tell. The crank has to be turned for the cam to line up each side of the oil galleries. View attachment 148854es.
View attachment 148856
View attachment 148853

The big block Chryslers that the right bank (2,4,6,8) will prime when #6 cylinder is on TDC and the left bank (1,3,5,7) will prime when #8 is at TDC.

 

[MILOJ]

Did you try a high pressure pump

 

[moparmike68]

Did you try a high pressure pump

Yes but no real difference.

 

[moparmike68]

This is what I would do before I take anything apart.

View attachment 150597
The big block Chryslers that the right bank (2,4,6,8) will prime when #6 cylinder is on TDC and the left bank (1,3,5,7) will prime when #8 is at TDC.View attachment 150599View attachment 150600

Think that is what I’m going to do , check for oil psi and that the oil is getting to the valve train.

 

[Former owner]

I'm curious about the "rebuild". What do you know about the bearing clearances? Were the cam bearings changed out? Why was the engine rebuilt in the first place? Did it have an oil related failure? Installing a high volume OP would be foolish in a 4 qt. sump. It could evacuate the sump under some conditions, and leave you pumping air. For what it's worth, I always ran Castrol 20w50 Racing Oil back in the day.
I would start diagnosis by subbing in a mechanical OP gauge, and get it up to operating temp. I agree that a hot idle pressure less than 15PSI is cause for concern, especially in a renewed engine. Absent other symptoms, you could just have a bad sender/switch. In any case, you'll need to know your numbers before swapping parts out. That can get expensive in a hurry. If I were to remove the pan, I would have some plastigage on hand, and check clearances on every rod and main cap. If you choose to do that, make sure all surfaces are dry when you check clearances. Remember to lube them (cam assembly lube is really good for this purpose) before reassembly. And I would not install that oil pump back into the engine! My rotors never looked like yours.

 

[moparmike68]

I'm curious about the "rebuild". What do you know about the bearing clearances? Were the cam bearings changed out? Why was the engine rebuilt in the first place? Did it have an oil related failure? Installing a high volume OP would be foolish in a 4 qt. sump. It could evacuate the sump under some conditions, and leave you pumping air. For what it's worth, I always ran Castrol 20w50 Racing Oil back in the day.
I would start diagnosis by subbing in a mechanical OP gauge, and get it up to operating temp. I agree that a hot idle pressure less than 15PSI is cause for concern, especially in a renewed engine. Absent other symptoms, you could just have a bad sender/switch. In any case, you'll need to know your numbers before swapping parts out. That can get expensive in a hurry. If I were to remove the pan, I would have some plastigage on hand, and check clearances on every rod and main cap. If you choose to do that, make sure all surfaces are dry when you check clearances. Remember to lube them (cam assembly lube is really good for this purpose) before reassembly. And I would not install that oil pump back into the engine! My rotors never looked like yours.

I bought the engine used a long time ago( sometime in the 90’s) did the usual gasket replacements here and there then just got it running. Drove it for awhile, and just had lots of issues with low oil pressure, carb issues, cooling issues. So I drove it rarely. In the mid 2000’s I had saved up the money and decided to have it rebuilt( thought the low oil issue was just because the engine was “tired” and worn). Took the engine to a builder/machine shop in a neighboring town. (that I found through word of mouth) took it to him and told him I wanted it rebuilt to stock specs. Told him I wanted the engine internals reassembled so that all I would have to do would be install the valve covers, intake , carb, timing chain cover etc myself. I assumed that the internals were all new and gone through. I didn’t get much info back with the engine(such as clearances , etc.) It was my first engine rebuild so I was not familiar with what to expect or ask for. I assumed that he was the “expert” and that he would do a good and thorough job. At this point I’m not sure what he did or didn’t do. I don’t know if he removed galley plugs and cleaned those circuits out or not. Nor if he plastigaged the bearings or if anything was done to the crank journals etc. I thought that the rebuild would fix my low oil pressure issues. But based on the fact that it didn’t, it’s a little concerning regarding his quality of work on the internals

 

[Challenger RTA]

This might be a possibility.

Understanding Engine Oil Aeration​

What is Engine Oil Aeration?​

Engine oil aeration occurs when air bubbles mix with engine oil, leading to a frothy or foamy consistency. This can disrupt the oil's ability to lubricate engine components effectively, resulting in increased wear and potential engine damage.

Causes of Engine Oil Aeration​

Several factors contribute to engine oil aeration:

• High Engine Speeds: Rapid engine revolutions can agitate the oil, introducing air bubbles.
• Improper Oil Levels: Overfilling or underfilling the oil reservoir can cause aeration. Overfilled oil can churn excessively, while underfilled oil may draw in air.
• Faulty Oil Pumps: Malfunctioning oil pumps can fail to maintain proper oil flow, allowing air to mix with the oil.
• Oil Quality: Low-quality oil or incompatible oil types can lack anti-foaming properties, increasing the risk of aeration.

Effects of Engine Oil Aeration​

Aerated oil can lead to several issues:

• Reduced Lubrication: Air bubbles disrupt the oil film, increasing friction and wear on engine parts.
• Engine Overheating: Aerated oil does not dissipate heat effectively, leading to higher temperatures and potential thermal degradation.
• Oil Degradation: Exposure to air accelerates oil oxidation, resulting in sludge and varnish formation.
• Pressure Loss: Aeration can cause cavitation in the oil pump, leading to a loss of oil pressure and potential oil starvation.

Prevention of Engine Oil Aeration​

To minimize aeration:

• Maintain proper oil levels.
• Use high-quality oil that meets manufacturer specifications.
• Regularly check and maintain oil pumps and lubrication systems.
• Avoid prolonged high-speed driving when possible.

Understanding and addressing engine oil aeration is crucial for maintaining engine health and performance.