Thread: OIL Pressure woes...

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It is my understanding from your posts this engine had good oil pressure to start and only started doing this after you started running it hard for the first time.

Two things could have happened. The bottom end is comming apart or the oil pump relief valve is stuck open. No you don't have a relief valve in the block. This relief is built into the pump.

If you never had good oil pressure from the start then other comments make sense.

Did you have metal in the oil when you did the oil change? If not I would rule out the bottom end going south. Stop running it till you have this figured out.

I personaly would drop the pan inspect the pickup then change the pump.

There were not metal flakes in the oil, no glitter or anything. I cut the filter apart and found nothing in the filter. The by-pass I was talking about is the one that is stock on the filter adapter. That has been removed in favor of a billet adapter for full-time filtration.

The relief valve in the pump is what I am kinda thinking MAY be a problem.

It started after I go the motor nice an warm from beating on it. It has not been driven in warmer temperatures since it was installed for more then 15 minutes as I work 3 miles from home. It got broken in while it was in the 50's outside so it got up to 185 and stayed there the whole time.

Suggestion on a good quality pump to have on stand-by... if I am gonna drop the pan I may as well swap in a different pump to further put my mind to ease.
Clay

by pass could be stuck but what is the max oil psi will it build ? if its over 50 then by pass is not stuck open and you did say it builds oil psi when you hit the gas ? if so its not the oil pump by pass. you did say cold it builds more idle psi ? then hot if so then its heat . if all this is wrong and this is new deal and its now low oil psi where it was hi before and temp is the same then somthing is going away

it will build to 60 cold. it builds psi when you get on it. cold it idles at 50.

so heat it is. kinda sucks, i bought an 8 quart pan to get more capacity to fight the heat. guess i need to run a cooler on it...

will a cooler pull my pressure down more though?

Originally Posted by jeepman1320

it will build to 60 cold. it builds psi when you get on it. cold it idles at 50.

so heat it is. kinda sucks, i bought an 8 quart pan to get more capacity to fight the heat. guess i need to run a cooler on it...

will a cooler pull my pressure down more though?

well that has to do with hose size .and voume of oil cooler comes in play i would think. if this thing makes 40 psi at 4000. and makes 50to 60 max at wot live with it .i thinking you have 3 + on mains and rods and if king hp the rear main is at 004+. so hot she drops has the oil thins out . you could by the mellings mel 10778 and you can adjust the by pass in the oil pump but that may not help alot

This is just for conversation and nothing more.

We built a chevy 454 years ago. Rods at .0025 Mains at .0028.

Had an Melling HV pump in it on the stand and started playing with the pressure relief spring in the pump. We would spin the pump and watch the pressure readings after adding shims. Kept adding shims pressure went up and up.

We wanted to see where it would just give up and produce no higher pressure. We were shocked to see over 250 psi. This is with a spacer we finally installed to limit the relief to just lift off the seat in the pump and no more. This was on the stand now, not running but we would rotate the crank.

My point is the pump is capable of producing high pressure.

You never mentioned what the oil pressure in yours was on the first fire up.

Good luck my friend, I hope you get her figured out!

well you should check the oil at temp and the rpm of the oil pump at idle so if at 1000 rpms 1/2 crank speed is 500 rpm s so you will see what for oil psi ? you can shim the by pass i used a 080 shim on loose engines but at ilde the by pass may not come in to play i started to make a oil pump test stand and you could test yours up to a new pump or shim yours as you know what yours is in you engine to adjust the pump. like jerry said it really need to be on the engine less you make a test stand . as for were i set rods and mains like i said i have used many sets of kings and if your at 003+ on mains number5 will be at 004+ and rods are at 003 your going to have what you have i know i been there done that my 632 donovan is some what like yours cold 60+ at idle and hot 20 builds hot to 60 psi engine been to 8000 many times so why would you think you need more oil psi at idle ? my old 572 the kid re bearing it so when it came back to a rebuild i check the rods were at 004 mains were 003.5 did have a low idle but did build oil psi never lost and bearing and they were going to past 7500 in mud pits . so can you jam the by pass yes it a gear pump and you can blow the oil filter case off if over shimed . you need to know when the by pass start to work have a hard time thinking it open up fast with hot oil giving you low oil psi. then cold thicker oil and more psi ? so you may shim the pump. do you want to stuff shim under the spring to get 40 hot at idle ?? so the double what you have now hot .so cold this thing could have ??? 100 psi if you say you have 50 at idle cold ??? i really never played with spring in pumps i blue print the pump clean the by pass and put it on . i cut goove s in the pump bodys .now i just buy them set the well and bolt them on i built many bbc and the ones that had low oil psi i knew would before the oil pan went on has i check to .0001. CV make s a out side bypass you can adjust with a stock oil pump but you need to block the by pass in the oil pump. i spend alot of time on bearings .more then i ever did and where i set the mains and rods for street strip stuff i have a good idea what the oil psi is going to be it

I would be comfortable with a consistent 20psi. I know volume it more important than pressure. I am guessing that is why when my oil was "dropping" to 0 but I was not getting any oil starvation sounds.

The motor is in a rock crawler, not a mud bogger, so it sees a bunch of off idle beating/full-throttle hits. That is why I am concerned about low idle pressure, but with 20w-50 I am seeing better pressure once it gets hot.

I think your original idea of it being from getting too hot is right on the money. I am going to go ahead a swap pumps out though since after doing a ton of reading it seems that the m-77hv is not what it used to be with powdered metal gears and horrible factory tolerances.

Clay

Originally Posted by jeepman1320

I would be comfortable with a consistent 20psi. I know volume it more important than pressure. I am guessing that is why when my oil was "dropping" to 0 but I was not getting any oil starvation sounds.

The motor is in a rock crawler, not a mud bogger, so it sees a bunch of off idle beating/full-throttle hits. That is why I am concerned about low idle pressure, but with 20w-50 I am seeing better pressure once it gets hot.

I think your original idea of it being from getting too hot is right on the money. I am going to go ahead a swap pumps out though since after doing a ton of reading it seems that the m-77hv is not what it used to be with powdered metal gears and horrible factory tolerances.

Clay

well they are ok that is why i look them over and fine tune the well . there alot of B.S out nothing wrong with powdered metal ,it is used alot more then you or some would think. the mellings pumps where so ,,so five years ago there abit better now. if you want try another make i all ways use m-77hv or there race oil pump . i had gm test a m-77hv and a hand built gm pump both were tested at gm it did not make much dif . i have used 100s of melling pumps i not had to much to talk about they work ok you can pay more for another name on the same oil pump?

Do you have a pcv???? is it working correctly? how much vacume in the crankcase at idle???

You said that you don't have the by pass valve in filter mount???

And you have some header tubes that are close to the sump??

620 idle, 310 pump rpm, HOT thin oil, loose clearances, time is a constant, oil pump rate low per time, differential pressure drop across filter(no by pass) and a pcv creating crankcase vacume will cause pressure indicated on guage to be low as compared to flow.

If you want to see how much oil will pump at that rpm take a varible speed drill at about 300 rpm and drive a pump with it in a bucket of oil--you'll be surprised at how much and how far it'll squirt!!!!!

It has a does not have a PVC on it. It has a vacuum hose to a breather and a hose from the other valve cover to the air ceaner...via total seal recommendations. It runs 10-12inches of vacuum in crankcase.

take of the vacume hose and your low oil pressure indication at low idle speeds will go away( maybe also need to put the oil filter bypass valve back in.

We are running some comp eliminator engines with a lot of crankcase vacume and the oil pressure guage will be low reading or negative!!!!

10-12 inches of vacume could suck oil thru a sump pipe into the oil galley and lube your engine.

so as long as I am seeing plenty of oil up top then the extra vacuum could just be play tricks on the gauge? hmm, wonder if there is way to measure volume instead of pressure...

Just wondering. 8 quart pan. How far is your pickup off the bottom of the pan?

Originally Posted by jeepman1320

so as long as I am seeing plenty of oil up top then the extra vacuum could just be play tricks on the gauge? hmm, wonder if there is way to measure volume instead of pressure...

pressure is the resistance of volume/ back pressure thinner oil less resistance . more cleance s less resistance