Oil pump bypass spring ??

[gkent]

How much pressure does it take to get the bypass piston to actually move ?? I've been chasing a low pressure at idle gremlin and I've read posts elsewhere where guys are using adjustable screws, shims, etc. to solve this issue and it makes no sense to me at all. The point of the bypass is to limit the max pressure only. Seems to me that spring will hold the piston till upwards of 50 psi before the piston budges. Fiddling with the bypass would be totally pointless to resolve low rpm pressure.

 

[hunt2elk]

Fiddling with the bypass would be totally pointless to resolve low rpm pressure.

That is correct.

 

[WileE]

If the spring is worn or broken, it could cause low pressure.

 

[toolmanmike]

There used to be kits with stiffer or longer springs to increase the pressure. It's a band aid if you have worn bearings.

 

[Daves69]

...........Fiddling with the bypass would be totally pointless to resolve low rpm pressure.

Maybe the poppet is hanging up in the bore.

 

[toolmanmike]

AI description.
AI Overview

A Mopar 383 oil pump system typically uses a pressure regulator valve, often called a pressure relief valve, which is located within the oil pump itself to control and release excess oil pressure. While oil filters have their own bypass valves for when the filter is clogged, the 383 oil pump's design features a specific valve to prevent excessive pressure from reaching the engine's lubrication system.

The valve seals the passageway and the spring regulates the pressure. When the pressure get's too high, it overtakes the spring pressure and unseats the valve to bypass.

Shim the spring a bit and report back with your pressure increase.

 

[R413]

Whether you agree or not putting washers in the cap will increase the maximum oil pressure.

 

[toolmanmike]

Are we talking big blocks here? If not, there are kits for small blocks as well. https://www.classicindustries.com/p...yFHa0qDlKU6NhJ9i8uaDsKK9g452It1xoC55MQAvD_BwE

 

[dvw]

If the valve was stuck pressure would be low all the time. The spring has nothing to do with idle pressure. There isn’t enough flow at idle to create any resistance. Thus the bypass is shut. If idle pressure is low there are 4 cures. Thicker oil, lower oil temp, higher volume pump, less internal leakage. How low is it? If it’s 15 psi there is zero reason to be concerned.
Doug

 

[rickseeman]

I've been chasing a low pressure at idle gremlin

The engines in our classic Mopar muscle cars are over 50 years old. There are problems associated with this. One recurring theme you will hear about on the forums is “low hot oil pressure”. Yes it’s true, you have low hot oil pressure. Don’t panic. Your engine is not going to “blow up”. It will still make plenty of oil pressure when you are driving because the oil pump is turning more rpm’s. But when you are idling the engine might be turning as low as 700 rpm’s. That means your oil pump is turning 350 rpm’s. Engines wear. This wear causes the clearances between the parts to become larger. Sooner or later the clearances between the 5 main bearings, 8 rod bearings, 5 cam bearings and 16 lifters will become large enough that the volume of the stock oil pump at 350-400 rpms isn’t enough volume to build the pressure it used to have when the oil gets hot, so the pressure builds to less psi than when new. There are ways to solve this problem. Sometimes you can just idle the engine up. That will help a lot. If that’s not possible you can go to a heavier oil. People have been running 50w in Mopars for 60 years. If that doesn’t fix it you can install a Melling M-63HV high volume oil pump. It looks like the stock M-63 Mopar oil pump on your car but the rotors are around ¼” longer to give you 25% more volume. It’s only 4 bolts to replace and it is fairly simple, but I would use ¼” longer bolts to put the HV pump on. By this time your “low hot oil pressure” problem should be fixed and the world will be a better place to live.

 

[toolmanmike]

The engines in our classic Mopar muscle cars are over 50 years old. There are problems associated with this. One recurring theme you will hear about on the forums is “low hot oil pressure”. Yes it’s true, you have low hot oil pressure. Don’t panic. Your engine is not going to “blow up”. It will still make plenty of oil pressure when you are driving because the oil pump is turning more rpm’s. But when you are idling the engine might be turning as low as 700 rpm’s. That means your oil pump is turning 350 rpm’s. Engines wear. This wear causes the clearances between the parts to become larger. Sooner or later the clearances between the 5 main bearings, 8 rod bearings, 5 cam bearings and 16 lifters will become large enough that the volume of the stock oil pump at 350-400 rpms isn’t enough volume to build the pressure it used to have when the oil gets hot, so the pressure builds to less psi than when new. There are ways to solve this problem. Sometimes you can just idle the engine up. That will help a lot. If that’s not possible you can go to a heavier oil. People have been running 50w in Mopars for 60 years. If that doesn’t fix it you can install a Melling M-63HV high volume oil pump. It looks like the stock M-63 Mopar oil pump on your car but the rotors are around ¼” longer to give you 25% more volume. It’s only 4 bolts to replace and it is fairly simple, but I would use ¼” longer bolts to put the HV pump on. By this time your “low hot oil pressure” problem should be fixed and the world will be a better place to live.

Low oil pressure at idle. When I worked at the Buick dealer we had those issues with many of the older Buick built engines. The oil lights would flicker at idle hot. We had a zero pressure sender that wouldn't turn the light on until no pressure. It was used a lot on used cars. LOL

 

[PRHeads]

This topic comes up all the time, and I used to debate about when the pressure valve starts to open.
I’m tired of having that argument, so I’ll just leave you with this…..
Having experienced first hand what happens when the relief valve is stuck completely shut, my assessment is that unless there is a massive “leak” in the system down stream of the pump, the relief valve is open, at least to some degree, all of the time(cuz when it’s stuck shut you’ll see oil pressure you didn’t think was possible).

Shims and/or a different spring in BB always worked for me.

 

[gkent]

Ok, I didn't menton it earlier BUT this is a fresh build - all new, 526 stroker. Solid roller cam, HS roller rockers. Idle at 1000 rpm with 30 wt "break in" oil yields 10 psi when warmed up. HV pump. I figure the lifters and rockers are the cause of low oil pressure - or at least a main contributor.

I'm "considering" switching to 20w50 oil but the motor has less than an hour run time on it. Concerned 20w50 won't give the rings the opportunity to seat properly.

 

[PRHeads]

did you check to see how much leakage there is coming out around the bottoms of the lifters throughout the travel while priming?
I’ve seen some that were serious leakers.

A couple years ago, we freshened a 440 and converted it from a SFT to a HR cam.
This engine always had good oil pressure before the freshening.
Some debris had gone thru the pump so it got replaced.
Oil pressure was notably lower than it was previously.
We swapped the spring out of the new pump for the one in the old pump.
The old one was obviously stiffer…….oil pressure problem solved.

I’d do the easiest thing first.
Shim the spring. If that shows any improvement, replace the spring.

 

[gkent]

did you check to see how much leakage there is coming out around the bottoms of the lifters throughout the travel while priming?

Yes, I noticed that very early in the build and ordered and installed "shrouded" lifters. And the cam can be considered "mild" for a sold roller - only .600 lift at the valves. Regardless, they do bleed a lot of oil there still - and the clearances aren't out of spec.

 

[PRHeads]

HV pump?
How high does the pressure get at like 6k when it’s all heated up?

 

[gkent]

HV pump and it pretty much maintains 10 psi per 1000 rpm. Problem is only at idle.