Low peak oil pressure

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turbovan

turbovan

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Hello,
I have a new build with oil pressure acting a bit strangely. I suspect a pressure relief valve issue, but I was hoping to get some input.
The engine has less than 300 miles on it, but was assembled over a year ago and unfortunately the build notes were lost in a move so some of this information is coming from someone with poor memory. New crank, new rods, and new HV oil pump(I believe sealed power). The oil pump was gone through, ported/smoothed, and mopar high pressure spring added. I do not have or remember the bearing clearances, but I initially installed Clevite HGX bearings to set everything up on the looser end around .0025(I believe).

Kevco 5qt pan and pickup. 12an lines from block to oil filter/cooler.

Upon initial priming with a drill, I think* I saw 70psi. During break in I was seeing 20psi hot idle, and 45-50psi at 35-4000rpm. Oil pressure did not seem to rise above that, and cold oil pressure was 50 at startup. This pressure was seen on a mechanical gauge. An electric gauge was installed and readings verified.

I dropped the pan and inspected everything. It all looked good, but I decided to swap out main bearings for standard non extra clearance to see if it helped with pressure. Verified rear galley plug was installed, and pulled the pump to verify the inner block plug was installed above it. No real change was seen, and I’m seeing around 55psi max from 2500-5500rpm. Pressure does not rise after 2500rpm. 20-25psi hot idle, and 60 psi cold idle.

Currently running VR1 20w-50. I ran 5w-30 for a short time with very little difference in pressures: maybe 5psi less hot idle.

Cam lobe lift is 377/352 with magnum roller lifters so hopefully not pushing them too high and causing a leak.

What should I be checking next? I do have a box stock melling hv pump sitting here that I am considering installing.
 
My suggestion would be to use an inspection camera in the valley area while priming to see if that lobe lift/lifter pairing(pre-magnum block?….actually, it has to be a magnum block to use those lifters…….right?) is causing excessive leakage around the lifters.
(More lift is created by lowering the base circle, so the lifters would be lower in the bores when the valves are closed, which could creat a path for oil flow from the oil band out the bottom of the lifter bore)

Probably need a helper to turn the motor over while using the camera.
 
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Sometimes problems occur at oil pump to rear main fitment.Gasket,no gasket,pump not seating on cap properly etc
 
turbovan said:
Hello,
I have a new build with oil pressure acting a bit strangely. I suspect a pressure relief valve issue, but I was hoping to get some input.
The engine has less than 300 miles on it, but was assembled over a year ago and unfortunately the build notes were lost in a move so some of this information is coming from someone with poor memory. New crank, new rods, and new HV oil pump(I believe sealed power). The oil pump was gone through, ported/smoothed, and mopar high pressure spring added. I do not have or remember the bearing clearances, but I initially installed Clevite HGX bearings to set everything up on the looser end around .0025(I believe).

Kevco 5qt pan and pickup. 12an lines from block to oil filter/cooler.

Upon initial priming with a drill, I think* I saw 70psi. During break in I was seeing 20psi hot idle, and 45-50psi at 35-4000rpm. Oil pressure did not seem to rise above that, and cold oil pressure was 50 at startup. This pressure was seen on a mechanical gauge. An electric gauge was installed and readings verified.

I dropped the pan and inspected everything. It all looked good, but I decided to swap out main bearings for standard non extra clearance to see if it helped with pressure. Verified rear galley plug was installed, and pulled the pump to verify the inner block plug was installed above it. No real change was seen, and I’m seeing around 55psi max from 2500-5500rpm. Pressure does not rise after 2500rpm. 20-25psi hot idle, and 60 psi cold idle.

Currently running VR1 20w-50. I ran 5w-30 for a short time with very little difference in pressures: maybe 5psi less hot idle.

Cam lobe lift is 377/352 with magnum roller lifters so hopefully not pushing them too high and causing a leak.

What should I be checking next? I do have a box stock melling hv pump sitting here that I am considering installing.
Click to expand...
I'd look at the remote filter. Years ago a bud with a 428 Fairlane lost around 30lbs after installing one.
 
I have considered looping the oil lines to bypass the filter/cooler temporarily to see if pressure improves. I did smooth out the filter housing transitions to help with flow.

Oil pump was port matched to the rear bearing cap, both are flat, and it has a gasket. Pump has also been removed and reinstalled since the problem started without any changes.

I will definitely throw a camera into the valley and look for leaks. Magnum block. Here’s the cam data if it matters.

IMG_0094.jpeg
 
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It’s been my assumption that a leak or restriction would lower overall pressure, but that it would still rise linearly with rpm? Pressure comes up fast and just flatlines.
 
Well, at least you gave enough clues we can guess the application is a small block.
 
There were some pumps, Melling I think that had the cup plug on the pressure reg spring installed backwards.don’t remember particulars.Probably no account,but never no.You said you added a HP spring,you sure the cup is positioned properly.If I remember correctly the spring sits against the flat of the cup.
 
Remember this. A high volume oil pump is not a high pressure oil pump. For some applications, you can get pumps that are both, but not for Mopar. Mopar Performance used to sell HV Melling pumps under the MP name that were modified with the high pressure spring making them both high volume and high pressure. You can do the same thing by installing a high pressure spring.
 
Outasite said:
There were some pumps, Melling I think that had the cup plug on the pressure reg spring installed backwards.don’t remember particulars.Probably no account,but never no.You said you added a HP spring,you sure the cup is positioned properly.If I remember correctly the spring sits against the flat of the cup.
Click to expand...
How to Install a High Press Spring in a Small Block Oil Pump

I believe it’s positioned with the spring IN the cup. The spring is also positioned inside the cup on the, extra, new Melling pump I have.

IMG_2146.jpeg


IMG_2147.jpeg


The second pic is a bit deceiving. The plug “face” is outwards so that the spring is sitting inside the cup. The shiny part above the plug is just machined metal on the pump. The plug is pushed down(maybe too far) below the pin.

So is the cup direction on this pump correct or is this one of the melling mistakes?
 
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I’m sure someone will confirm or deny.But it’s my belief the spring sits on the “face” of the cup.NOT inside the cup.
 
I have an untouched used small block pump in the shop. I'll go look. It's not an HV pump but that shouldn't matter. brb
 
The closed end of the cup faces out against the cotter pin with the cup on the inside with the spring inside the cup.
 
turbovan said:
How to Install a High Press Spring in a Small Block Oil Pump

I believe it’s positioned with the spring IN the cup. The spring is also positioned inside the cup on the, extra, new Melling pump I have.

View attachment 1716226108

View attachment 1716226109

The second pic is a bit deceiving. The plug “face” is outwards so that the spring is sitting inside the cup. The shiny part above the plug is just machined metal on the pump. The plug is pushed down(maybe too far) below the pin.

So is the cup direction on this pump correct or is this one of the melling mistakes?
Click to expand...
Yup, that is the correct way to do it in Karl's how to.
 
I don’t want to hurt the motor so I’m going to end up pulling it to check things out “the right way.”

Will I be able to build sufficient testing pressure with a corded drill, or does it depend on the drill? What pressure am I looking for on the stand with what oil? I’m thinking I’ll aim for 75 with 10w30.

And I failed to note idle rpm in this thread. I was seeing 20-25psi hot at 7-750rpm.

Thank you all very much for the help. I couldn’t have built my car without this forum.
 
I was able to build up to 50psi on a cheap harbor freight drill, IIRC. It did kill the drill though lol.
 
Just recently did mine.408 with all the GJ oiling mods.10/30 break in oil,Melling HV pump,3/8 electric drill got 75 PSI constant pressure.when drill stops takes about 3-4 seconds for oil pressure to bleed off.Restart drill should have instant oil pressure.
 
Thank you both. Looks like there will be obvious discrepancies so I’ll prime it before pulling, and use the same oil so that I’m not changing other variables.
 
your numbers are fine- my 418 Stroker is fresh maybe 200-300 miles, Melling pump in that runs 20-25 hot idle and 55psi cruising under load. Cold start is probably a hit higher around 65 I’d say. I run 10-40
 
Does the relief valve move freely in the pump housing? That’s the next thing I’d check. Sounds like it’s stuck open. Then I’d pull the intake and prime it, watch for leaks around the lifters. If I saw nothing that worried me I’d be checking rod/mains clearance.
 
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