OIL Pressure woes...

Ok, I think I may have a problem.

Yesterday I decided to run this 468 hard and see if everything would hold together. :LOL: After a few hard runs through the gears and about a 15 minute drive at 3600rpm at 65mph (its a jeep thing and low gears don't help) I experienced a problem. I exited the highway and came to a light, when I put the clutch in to wait on the light to go green I checked all my gauges. Oil pressure was holding at about 18psi, which I thought was odd. I continued to watch the pressure and it dropped to 0! Gave the gas a little tap and it came up to 40psi, then settled back to 22 psi for a second then dropped to 0 again! I used my hand throttle to set the idle to about 850 rpm which netted me about 22 psi and I limped it home.

It never gave me physical indications that it was low on oil pressure, no lifter taps or anything like that. So I pulled the electric sender out and hooked up my manual gauge to it and changed the oil to check for gas , water, or bearing material, none of which were there. I run 15w-40 Rotella-T and a 51060 Wix filter.

I let it sit overnight to make sure it was cool and got 50 psi at 620 rpm cold, and 60 psi at 1400 rpm cold.

After I let it get up to operating temperature I took it out and beat on it some more to get the oil nice and heat soaked, brought it back to the garage and got 14 psi at 630 rpm hot, 42 psi at 1400 rpm hot, and 50 psi at 2600 rpm hot. I could not get it to duplicate loosing all oil pressure, but this could be due to it being about 15 degrees cooler today then yesterday.

I installed a brand new Melling M-77HV oil pump when I put the motor together. I am a little concerned that I may have gotten a bad pump. Does this sound about right? I was thinking about buying a Milodon pump to have on hand when I drop the pan to inspect the bottom end for damage.

I can not find my sheet with all my clearances written down, but if it were bearings I would expect to see less pressure being made when its revved. Or am I mistaken?
Thanks,
Clay

Where is your sending unit mounted. My BBC is in the low 20+ range when hot. I have an electric sender mounted above the oil filter very close to the exhaust manifold. I am wondering if that has something to do with mine. What cam did you go with when you rebuilt? Your saying you can idle around 630rpm? I am in the 850 to 900 range with an RV cam. You may be low on your idle speed! I may be high?

Stock oil pan? HV pumps and 3000+ rpms empty stock pans

oil pressure sender is above the oil filter.

Hamburger 8 quart oil pan with baffles and windage tray.

it has a Lunati retro-roller 60211 in it if I remember right.
.575/.575 lift 272/280 advertised duration 112 seperation

well some think you need 10 pounds for every 1000 rpm s but if you live by this and i do not then at 1000 rmp you need only 10 psi and need 70 at 7000..i think your oil is getting to hot and you may be loose on mains and rods so hot it going to be low hot 20 is fine .when cold it about 40+? long as it builds oil psi under a load .try another oil gauge with a 3/16 line kit

You could have a stuck pressure relief plunger in the oil pump.

maybe throw an oil cooler on it to keep it from getting so hot?

My first thoughts were what 53 Willys said, you are sucking the pan dry. Maybe try a straight weight oil in the 30-40 wt range. I run Rotella T 15-40 also, and I am noticing a little less oil pressure in my 331 Ford at idle than I got with straight 30, but that could be other factors too.

Don

well bbc have good drain back even with a stock pan with a hv pump a short blast you not sucking the pan dry . on race engine 20w50w val or straight 40w is what i like as long as it warmed up good be for you beat on it . i use the brad pen 40w . i would stick by the oil getting hot as well . i build alot of bbc so i should know . soon has my skin grows on my back i be building more :)i know where to set the mains and rods so i do not get calls on low oil PSI . by pass could of got hanged up .the oil could of been breaking down as well

i think the mains and rods are at .002 or .003, but .003 sounds more familiar. I don't remember which. I will try running a straight 40 weight oil. Oil is cheap, bearings are not. I don't drive em hard cold so it should not be an issue. I will post up the results later today.
Clay

A defective oil filter can play games with oil pressure. They're relatively cheap, and easy to change. Try another brand.

Just got done beating the dag stuff outa it after switching to 20w-50 val. oil pressure is still not to bueno. at hot idle it fluctuates between 16psi and 18psi. usually at 16 more, but will pop up to 18 every once and a while. call it a day or tear the pan off and put a different pump on it?
Clay

there are lots of things that will effect oil pressure on builds even with the right clearances and oil pump/filter/pickup/pan choices---

besides the choice of what lifter, rockers and up top stuff---distributor fit in the hole(o-rings around base) loose or missing or too large a bleed hole in the front galley plugs--
champered cranf oil holes that are misplaced

oil picpup that has fallen out of the pump, pick up against bottom of pan, pressure relief valve backwards, etc

IF YOU PULL THE PAN---check each and every bearing including the thrust ----

if your brave---with the oil pump removed you can pressurize the oil gallies with compressed air and see if you notice an area where there is unusual differance in the blow out

good luck and hopefully something simple($$$$imple)

yep you can do the O ring deal but that will not help . been there done that on a573 and a 462 that was doing the same. but bottom end was set up very loose .so yes every thing jerry said i would go along with . as for your pump if junk went thru it then it will open up . try another pump but it idle is low but builds sound like a loose bottom end were i set them street is not the same as track long as its 60 at WOT no need to worry about this is not much load on ilde i had them so loose you could hear the crank drop on idle :) seen them with 10 psi at a idle hot

Well, I am currently using a WIX 51060 filter, from what I have heard they have a bypass spring in them as well that may effect oil pressure with thicker oils so I may try a different filter, say a K&N or something similar.

I did notice that I as soon as I get off idle it build to 35psi. Just seem weird that it is only low at idle, but has good pressure everywhere else even with thinner oil. At first I thought I was in the clear because it held about 30psi after a few good runs, but then it just came back down.

Up top I am using Lunati street performance retro roller lifters, with Comp-Cams high-tech 3/8" push rods, and Comp-Cams steel roller tip rocker arms. Nothing super fancy, but it works.

The pick-up bolted onto the pump, and if you are talking about the bypass in the block above the filter... I don't have one.

I am thinking about installing an oil cooler on it now as that seems to be the most likely culprit at this point. It does not help that this motor is shoe horned into a Jeep Scrambler. Everything is super tight and the driver side exhaust wraps around the front of the sump tucked up pretty tight to the pan. There is maybe 1.25" of airspace between the pipe and pan. The motor never runs above 200, but I have a feeling that the under-hood temps are up there pretty close to engine temps.

Ah the joys of having toys! Thanks for all the help and suggestions, I will continue to try to figure this out. If I am gonna drop the pan it will have to wait because everyone is out of stock on the pan gasket for the pan I have.

Any suggestions for a GOOD high volume oil pump so I can have one on hand? I was looking at Moroso since they already have the anti-cavitation grooves cut in em, but I am not sure. If I drop the pan it will be with the motor in the Jeep so I will have to Plasti-gage the bearings, but I guess that is better than nothing.

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?

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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?

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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

Quote:

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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

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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?

Quote:

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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...

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

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Originally Posted by sfort

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

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Its 1/4" off the bottom.

Quote:

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Originally Posted by sfort

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

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pan could hold 5 quarts to 12 the pickup needs to be 3/8 to no more then 1/2 from bottom of pan 1/4 with out pan gasket

Quote:

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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...

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i have a very hard time buying this if only 12 inchs but very EZ to check pull pcv and plug it run it down the road with open breathers one on each valve cover

Jeepman, Been a while. Did you ever figure out your oil pressure woe's?

The new oil pump helped a bit, I also used a dead soft copper shim between the new pump and main cap. I also wrapped the crossover pipe under the pan to help keep the heat off the pan. It will maintain 20+ warm, but I am running 20w-50 Valvoline. I am still slightly concerned about how it will do during the summer months when we see some real heat an not just 70 degrees.

I think I'd bump the idle up a bit. 630 rpm seems a bit on the low side. I could be wrong but it seems I remember the idle on the stock big blocks was usually somewhere around 750 rpm.

Jeepman 1320. Where are you getting your reading from. Is your sending unit at the filter? I get similar readings and I am getting the readings at that location. I have very little clearance (around a quarter inch or less) between the exhaust manifold and nipple coming out of the block that the sending unit attaches to. My idle runs about the same as yours and pressure readings get below 20psi when hot at idle. I am running 10w30 now last summer 20w50 without a big change. I am going to try to get the sending unit fitting farther away from the exhaust. My assumption is the I am heating the oil before it gets to the sending unit. It stays hot because that is a dead end so there is no circulation. When you rev the engine it counter acts or does it's job and shows a pressure increase. Also I am going to bump my idle up closer to 750 rpm (makes sense).