Thread: OIL Pressure woes...

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Ok, I think I may have a problem.

Yesterday I decided to run this 468 hard and see if everything would hold together. 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.