Help with low oil pressure

[moparmike68]

need help please.
I have a low pressure issue that I have been dealing with for a while. It’s 383 magnum rebuilt and has less than 1000 miles on it. Had low oil pressure issues before rebuild and still have similar issue after rebuild. Currently has new stock m63 standard pressure pump. (Tried a high volume pump but made no difference). I have an oil pressure gauge and dash light connected. Has ok pressure when starting out but once the oil gets hot the pressure drops to 10psi or lower at idle or at a stop light. Recently the oil light started to flicker when I pulled up to my house, so I quickly put it in the garage and haven’t had the stomach to tackle the problem. I have a new after market dip stick (because the original one had the grab loop break off) I did make sure that the dipstick was the same length stowed as the original. 1)Thought maybe I didn’t have enough oil in the pan (oil starvation)even though the dip stick registered full. 2) have been running 10w30 Brad penn hddp oil since break in oil was changed. Just bought some straight 40 weight oil because I read somewhere that straight weight oil keeps its viscosity better when hot than the mixed weight oils? Just drained oil and it appears that I have 4-3/4 qts which either the oil left in the engine and oil filter should be about right for the 5 qts capacity the manual calls for(it’s a stock pan with windage tray)
Question: I removed the oil pump and took it apart. Very clean, no blockages anywhere BUT there are a few small nicks or depressions nothing larger than a pin head and most are in the center of the inner and outer rotor faces. Could these small nicks cause significant pressure loss? Any help suggests would be appreciated. Also let me know if you need further clarifying info.
Thanks
Mike

 

[Daves69]

.......Could these small nicks cause significant pressure loss?......

That's pretty typical for a pressed powder metal gerotor. I'm pretty sure it's not the issue as you've seen the same with a different pump.

How hot is your engine getting?
Does your oil appear frothy as in aerated?
Did the engine rebuild include listing of the clearances?
You might change your oil filter. Cut the old one and see what it has been collecting.

 

[moparmike68]

That's pretty typical for a pressed powder metal gerotor. I'm pretty sure it's not the issue as you've seen the same with a different pump.

How hot is your engine getting?
Does your oil appear frothy as in aerated?
Did the engine rebuild include listing of the clearances?
You might change your oil filter. Cut the old one and see what it has been collecting.

Thanks for your reply. No over heating problems. New radiator etc . Oil is not frothy, is somewhat dark, but still has some greenish color of the oil( was green colored when new) No noticeable metal flakes or silvery particles at all in oil. I will cut filter open to see. I only use Wix or Napa filters. As far as the rebuild and included documentation there was no paperwork showing the tolerances etc. was a known rebuilder in the area, but I’m now having my doubts about how thorough he was. Not sure if he remove internal block oil passage plugs and cleaned passageways..

 

[HooToTheCore]

Did you replace the oil pickup? Make sure it is clear of debris and has clearance from the pan bottom.

 

[moparmike68]

Yes I am using the stock pan(402) and stock pickup. Not sure how to tell if it is touching the pan or not. Tried to look through the drain plug hole with camera, but cannot see a good view if the pickup. I really would rather not have to take the pan off since there are no leaks and it has a windage tray and possibly two gaskets. What a ***** to get off and back with no leaks.

 

[Daves69]

FWIW, a 402 is a 4 qt pan and add 1 more for the filter.
Not sure you'd see any oil pressure if any oil gallery plug is missing.
One confusing item on BB's is the rocker shaft oil hole correct orientation. These oiling holes for the rockers should be pointing down and out from the bolt centerline on both sides. You might check this.

 

[moparmike68]

Correct, that’s how I figured that I had the right amount of oil , as you said. 4 qts in pan plus what was left in the engine and oil filter. Thank you for the heads up on the rocket arm oil ports. I’ll check that out.
Thanks

 

[540HemiCuda]

What is you max hot oil pressure? If you have around 60 pounds HOT, you are okay there. Hot idle oil pressure around 15 pounds is also usually good.

 

[moparmike68]

FWIW, a 402 is a 4 qt pan and add 1 more for the filter.
Not sure you'd see any oil pressure if any oil gallery plug is missing.
One confusing item on BB's is the rocker shaft oil hole correct orientation. These oiling holes for the rockers should be pointing down and out from the bolt centerline on both sides. You might check this.

View attachment 150532

What is you max hot oil pressure? If you have around 60 pounds HOT, you are okay there. Hot idle oil pressure around 15 pounds is also usually good.

Hot idle got as low as 10 , can’t remember what hot max oil pressure was probably 40 +, but like I said it’s been a while since I drove it and don’t remember. I know of a friend that has an old truck, 67 power wagon with a 383 and it has good oil pressure 80 cold and probably 50-60 hot. I don’t believe it’s been rebuilt. The oil pump is new.🫩i

 

[540HemiCuda]

If you don't want to dig into the engine itself to diagnose what's going on, you have a couple of options that should help you get some more pressure. But first, make sure that you have an accurate measurement of your pressure and check to make sure that you don't have any lifter noise that would indicate that your pressure is so low that the lifters are collapsing.

Then, you can either install a hi volume pump (which is longer than the std pump), or you can try heavier weight oils. And you can adjust the pressure with the by pass spring in the pump. You can shorten the spring if your hot max pressure is too high or better yet, use a spring from a std pump. There used to be different rates of springs available and even an adjustable by pass pressure kit. And you can sometimes shim it if it is a bit too low. The spring is the only real difference between a std and a hi pressure pump. But that really is only for the max pressure (not idle) and you have to have enough flow even to do that. Remember that pressure is only a measure of resistance to flow. So you have to have enough flow to resist. And for most applications, much over 60 pounds HOT is just a waste. More is not better for street applications with no extraordinary demands.

And you can get senders with different actuation points. I use a 20 pound sender on a small red flashing LED indicator along with the factory gauge. That will hopefully give me a little more time to react should the pressure suddenly start dropping. I have done that since my racing days. You weren't watching the gauge going down the track, but that little flashing LED would get your attention.

.

.

 

[6PKRTSE]

It is probably fine as is. My buddy has an LS in his 1500 truck that has read 6 PSI at hot idle for years.

 

[540HemiCuda]

I wouldn't run hot idle oil pressure that low in our old dinosaurs. Modern engines have different internal clearances than ours. Likewise, most of our engines wouldn't like 0 weight oils.

 

[moparmike68]

If you don't want to dig into the engine itself to diagnose what's going on, you have a couple of options that should help you get some more pressure. But first, make sure that you have an accurate measurement of your pressure and check to make sure that you don't have any lifter noise that would indicate that your pressure is so low that the lifters are collapsing.

Then, you can either install a hi volume pump (which is longer than the std pump), or you can try heavier weight oils. And you can adjust the pressure with the by pass spring in the pump. You can shorten the spring if your hot max pressure is too high or better yet, use a spring from a std pump. There used to be different rates of springs available and even an adjustable by pass pressure kit. And you can sometimes shim it if it is a bit too low. The spring is the only real difference between a std and a hi pressure pump. But that really is only for the max pressure (not idle) and you have to have enough flow even to do that. Remember that pressure is only a measure of resistance to flow. So you have to have enough flow to resist. And for most applications, much over 60 pounds HOT is just a waste. More is not better for street applications with no extraordinary demands.

And you can get senders with different actuation points. I use a 20 pound sender on a small red flashing LED indicator along with the factory gauge. That will hopefully give me a little more time to react should the pressure suddenly start dropping. I have done that since my racing days. You weren't watching the gauge going down the track, but that little flashing LED would get your attention.

.

.

Yeah I’m more concerned about the idle pressure being so low. When I speed up, the pressure does increase, it’s just when I get to a stoplight with it in gear that it drops low and I just get panicked. I haven’t heard any noise like ticking that would indicate pump starving for oil, it’s just stressful . Thank you for your reply and info. I’m already going to try straight 40 weight conventional oil (valvoline racing oil with hddp)and see if that helps. Do you think synthetic oil would be better at keeping its viscosity?

 

[540HemiCuda]

No, I don't. I am not a fan of synthetics in our street cars. Trying 40 weight VR-1 is a good experiment. Probably the only real down side to long term use would be that the thicker oil just takes longer to get everywhere at cold start-ups. And that is why I use an Accusump as a preluber. The engine has oil pressure BEFORE I ever hit the key.

 

[moparmike68]

FWIW, a 402 is a 4 qt pan and add 1 more for the filter.
Not sure you'd see any oil pressure if any oil gallery plug is missing.
One confusing item on BB's is the rocker shaft oil hole correct orientation. These oiling holes for the rockers should be pointing down and out from the bolt centerline on both sides. You might check this.

View attachment 150532

If the oiling holes are in the wrong orientation, could that cause low oil pressure or just lack of lubrication to the valve train?