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.