So I got a huge problem. I had a shop build a 455 for me and now I am dynoing it. Melling oil pump. 24 psi @ 1800 rpm and 35 psi @ 3800...started wth 60 psi. VR1 10w-30. 8 qt pan. Mondello restrictors. Everyone says I should have 55 psi to include Mondello and Melling. Mondello is saying the Melling pump isn't strong enough. Dyno shop suspects tolerance issues. Engine shop says clearances are well within tolerances. I need help guys...

 

is the psi stay steady or does it flutter it higher Rpm? And is the pick up deep enough in the pan it may not be getting all the oil it can.

 

Why would the melling oil pump not be strong enough? Are they saying it's a bad pump or you need a more expensive pump? Makes me think clearance issues. I've heard bad oil filters can cause problems. Not a Fram?
Again is it steady or does the pressure jump up and down?

 

First off you don't need the restrictors, IMO. Secondly is the plug in the left rear lifter oil galley installed? Pull the distributor and look with a mirror. Look at the bypass plunger above the oil filter when removed...Make sure its seated. Make sure the oil filter didn't collapse. Always get a high quality filter...Wix,K&N etc. Hopefully the oil pick up tube is matched to the new pan?
24psi at 1800 is low. Whats it do at idle 5-10? This sounds like a classic case of the oil galley plug missing.

 

First step is to cut open the oil filter and see what it looks like.

 

PSI is relatively steady. Pickup was ordered with the pan to compliment it. I am not sure why the Melling pump would be not strong enough. It was the High Volume pump from Melling. M22-FHV. On paper, the pumps from Mondello and Melling seem the same. I have to check the lifter galley plug. I will call the shop to see if they have checked it yet.

 

Oil galley plug is installed with .030 hole drilled to lube distributor gear

 

Are you sure that the gauge is accurate?

 

Whats it do at idle 5-10psi? And yes is the gauge a known good gauge?

 

Can you post clearances, especially rod side clearance..

 

What they really mean is the Melling pump has it's limitations. But it should be more than adequate for your needs.
Drop the pan and check the relief spring. I've recently had one that was looser than others.
This last 455 I did had the same pump, Toro pan and the right clearances. It has 25psi at idle hot and 50+ during dyno pulls with 10W-30.
Conversely the DX I did had the same pump, same clearances and it had 35@idle and 70 during pulls with 10W-40.
Neither engine had restrictors.

Also what filter are you using? It won't make a 15psi difference unless it's defective but I'd like to know.

 

I searched around for Melling pumps and all I can find is "high volume, regular pressure" stuff. I asked Mondello what they did to their pumps and they said they modified the gears and increased the bypass spring strength so it bypasses at a higher pressure rather than a lower one.
Clearances are as follows:
Rod clearances: 0.020
Crank: 0.020
Main: 0.030
That's all I was passed by the builders. We didn't get to check it at idle, we ended up shutting it down. The gauge as far as I know was a good gauge. There was an analog as well as the dyno gauge and they were comparable.

 

The common practice is to shim the pump spring about 3/8".

I hope you mean .002 on the rod bearing clearance and .003 on the mains. Do you know if they even checked the clearances? And if so how?
Did you use studs or bolts on the mains?

Too many shops don't have a clue, whether it's a Chevy or an Olds, doesn't matter.

 

Sorry, .002 and .003. Was a little tired this morning. They built the engine from scratch and have had it apart and together twice and have definitely checked all the clearances. As for studs or bolts, I am unsure.

 

So the shop is lying to you OR your pump is junk from the get go. Either you or another shop will have to check clearances and see for yourself. I wouldn't let them touch it anymore at this point. Did they prime the oil pump with Vaseline when installed? Or possibly Owner error. DID YOU prime the engine with a drill before they started it on the dyno at all?

 

I'll bet you have something loose/missing, the pump is not square on the cap or spring/pump is defective.
Btw you don't need to prelube the pump with Vaseline.

 

Why would someone pack the oil pump with vasoline if your going to pre lube the engine with a drill and old distributor?

 

Kinda what I was thinking. That's an old "trick", not necessary imo.

 

The engine was primed with a priming "rod" prior to running on the dyno. The Melling pump is listed as a high volume pump, but standard pressure...

 

Anytime you try to push more volume thru the same size holes you will increase pressure. Plain and simple.

 

I personally just prime with the drill But I've know old timers to use Vaseline in the gears or fill them if they know it will be sitting for a long time. Just wonder if it didn't flush itself out yet if used. I'd think if it wasn't seated the PSI would flutter and not be a steady reading. When priming with a drill will it stop once you get to pressure? If the drill still wants to keep on turning I'd say loose clearances. Once you get to around 60 psi the drill wont want to turn anymore.

 

Hmmmm, I continue to spin mine once it hits 60 or so to make sure all the rockers have oil. Never had a drill stop once it hit 60.

 

^x2.

 

1 use a 12V cordless the torque is gone by 60 psi in the drill to keep spinning it. I've always heard if you can keep it spinning with a 12v drill the clearances are too big and blowing out the journals. And that's why I never use anything higher then a 12v drill.

 

Uhh there's absolutely no truth to that, that's total bullshyt.
Whoever told you that doesn't have a clue.

 

Agreed. Drills vary. A "12V" Snap-on drill will behave VERY differently from a 12V Shipwreck Tools "drill". That is just not sensible.

The cam cannot stop turning, and is geared to the oil pump, so whatever it takes to spin that pump must be provided by the engine. It can't "not turn."


"The engine was primed with a priming "rod" prior to running on the dyno. The Melling pump is listed as a high volume pump, but standard pressure...
.....
Anytime you try to push more volume thru the same size holes you will increase pressure. Plain and simple."
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Our scenario is NOT that simple. The pressure increases as you force fluid thru a system faster, sure, when a positive displacement pump is connected directly to the consumption system. Or, the flip side of that coin is that more pressure is required to attain more flow thru a given orifice/ system. Oil viscosity greatly affects the pressure, and hot oil is generally thinner than cold oil. Sometimes very much so- try to pour some straight 30 weight oil at temps below 20F or so sometime and you will see this readily.

...The system we are talking about here DOES have an oil pressure relief valve between the pump and the orifices. Once the delivery of the pump exceeds the flow consumed by the system - which happens basically at a certain RPM- then increasing the RPM of the engine/ pump causes the pump to produce more oil than the system can consume. The pressure builds up to the point that the relief valve opens, and the excess production is dumped back to the pump inlet.

Therefore, at any speed above the point where production exceeds demand, the system pressure should be steady and at the value set by the relief valve.... give or take a little.

My 403 has been very well behaved regarding oil pressure. Factory dash super accurate gage says it's about 20 at idle and close to 60 when driving, perhaps a little lower when warmer. I shimmed the OP spring a little, admittedly by guesswork, I think it was about 0.040" - 3/8" seems like a lot to me, asking for 100+ psi system pressure. But I defer to folks with more OP modifying experience than me.


"I asked Mondello what they did to their pumps and they said they modified the gears and increased the bypass spring strength so it bypasses at a higher pressure rather than a lower one."
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"Modified the gears" - that's pretty vague. Cryogenically treated? colored with crayons? Rubbed with dog dookie? Hardened? I see no reason to modify the OP gears in any way. MAYBE carefully alter the end clearance, IF you are good at it and know what you are doing. They typically have a pretty generous end clearance compared to say an Atlas-Copco air tool motor's rotor. The spring pressure simply sets the system operating pressure as set forth above.

Bear in mind that the pressure at which the pump operates is pushing back against the pump gears, requiring power from the engine. The longer the OP pumping gears, the more the effect of the pressure- and the more VOLUME the pump CAN provide... and DOES produce per revolution. An engine set up with loose clearances and not intended to be a family car for 20 yrs may well benefit from spending the power to run a HV pump at higher pressure, in order to ensure engine happiness with a generous flow of highly pressurized cooling, lubricating, cleansing oil thru all those crucial finely machined passages.

 

Shimming the pump 3/8" makes about a 10-12psi difference, apples to apples. Your .040 didn't do much. Just sayin.
And if you rev the motor quickly it'll pump more pressure than the relief valve can handle that quickly. You'll also see higher pressures when cold, even with a relief valve.
This last DX I did spiked to 70 then stayed at 55. But when cold you could add another 10 to that. The relief valves aren't perfect.

 

I would get me a new Mellings pump, high volume or not your choice, and start with that, I wouldn't like anyone messing with the gears in an oil pump.

 

And This is why I was told not to use a big drill. This way keeps the bypass closed in the pump. and if you can keep it spinning it's leaking somewhere else besides the pump. Sure I can put a huge drill on there and keep it spinning and more pressure but it's not going to help diagnose a leak.

 

i'll admit up front that i didn't read all the replies, but why do you think you have an oil pressure problem at all? unless that pressure drops below 10lbs at hot idle, its likely fine.

What you want are consistent readings- readings cold, and readings hot.
as long as you have a minimum of 10lbs oil pressure for every 1k rpm its spinning you should be fine.

Every motor especially after rebuulding depending on the clearances the machinst went with... is going to be a little different.

If pressure is lower than 10lb at hot idle, or pressure won't build with RPM, then I'd worry. Otherwise, just run it.

My $.02