LilJayV10

I am having a really strange, really bad oil pressure problem with the new engine i just built and installed. Cold start up@idle 65psi, warm@idle 40psi, cruising speeds, 55-60psi, part throttle accel, pressure drops to 40 and bounces back to 60, is extremely erratic. at wot, pressure goes up to 65+ then starts declining, when the engine hits about 4000rpm, the oil pressure drops to 0. I immediately take my foot off the gas, engine drops back down to idle, less than 2 second pressure jumps back up to 40psi. Driving the car around the pressure bounces around, but in park, I can rev the hell out of it and it goes up and down like it's supposed to.

Engine is rebuilt, 355, everything was plastiguaged, checked, so on. High volume oil pump, stock pan. Everyone will say thats the problem right there, hold on. A lot of people say a HV pump can suck a stock pan dry. I put an extra quart of oil in it to see if it made a difference, it didn't. Hard braking doesn't make a difference, a friend of mine, his 68 chevelle, the pick up tube came off the oil pump and under hard braking it would un cover the hole in the pump and the pressure would drop.

At wot, the pressure stays up untill around 4grand then it drops.

I did not weld the pick up tube on.

If the pump was sucking the pan dry, what is causing the flux in pressure at part throttle?

The engine hasn't made any bad noises, it's parked right now till I can find the problem.

I put a mechanical guage on it to verify the pressure readings.

These are the things I am wondering,

oil pump bad
pressure relief valve in oil filter housing, it has an oil cooler
dummy shaft that turns the oil pump is wore
pump suckin the pan dry

Any idea's? I'm at a total loss here.

Thanks
Jason

indieaz

high volume oil pump or stock? Stock pan or not? Possible your oil pressure sensor could be on the fritz as well. I find piece of mind in having an aftermarket oil pressure sensor so if they both read 0 then i know i REALLY have a prob.

FlyboyZ28

ttt for ya

97 RedSS

He has already verified the readings w/ mechanical guage..There are ALOT of people with this same issue on this board as I have seen numerous posts..I had the same problem after installing my 383 w/ a stock oil pan,HV oil pump and no windage tray.
I tried different oil/different filter/etc and nothing seemed to work..Mine would be around 55 cruising and it would flutter up and down sometimes but not all the time...When I went above 4k it would drop to around 40-45 so I stayed away from 4k...

I went w/ a Canton Oil pan and I checked the oil pump clearance and made sure it was correct depth...My issue improved alot when I went with this pan but ever once in a while it will drop slightly(~5psi)

My oil always looks good so I dont worry at all..As long as my motor runs strong I really dont care..It has been running 1.5 yrs and over 20k miles..

Cody

izzyz28

I'm having the same problem as well. Many people say the Canton pan will fix it, and others say the Milodon windage tray will fix it. I'm still waiting and hoping that someone will say a windage tray fixed the problem, but I have a feeling the Canton pan is a much better choice. I'd rather spend $300 on a pan than risk the $3,500 I have in engine parts. For those who are running the canton pan, what oil pump and pickup are you using?

FlyboyZ28

How is the oil pan going to make the difference? Is it because the current setup is sucking the pan dry? I thought it was said that an extra quart of oil was added to the car and it had the same problem. The car also doesnt do this in ever gear...just second gear around 4k.

indieaz

When i built my engine somebody (i don't remember who, maybe my machinist) told me not to run a high volume pump becuase it would run the factory pan dry. So i got a stocker and it seems to be working great.

Lonnie Pavtis

If the engine is sucking the pan dry, it will do it above a particular rpm in any gear or speed. Take the car to 4000 in first & hold it there without accelerating, does pressure drop?

The stock pan is terrible at oil control & the oil climbs the rear of the pan under acceleration uncovering the pickup. This is why it loses perssure in second, but not third. In first it may not have time to uncover the pickup before you shift. Generally at rpm more oil is pumped to the top of the motor as well as more oil being wrapped around the crank. This leaves less oil in the pan. This, coupled with acceleration forces making the remaining oil climb the rear of the pan, leaves no oil at the pickup.

Poor oil control coupled with a junk pan can even cause problems with a stock volume pump if the car accelerates hard enough.

1G acceleration force will cause the oil to stand at a 45deg angle in the pan. This is enough to lose pressure if nothing stops this motion. A good windage tray will return more oil to the pan by removing it from the crank & a baffle above the pump will stop this climbing action at the rear. This all helps. A Canton pan has a rear mounted pickup, placing it in the deepest oil under acceleration.

LilJayV10

I started taking the pan off tonight, i thought about how i was going to do it without having to take the whole damn car apart. What I have decided to try first is this, pick the engine up with a hose, i can raise it atleast 5 inches, there's quite a bit of room but not enough I'm sure, I was going to drop the whole k member out and just drop the pan down. I think i can undo some wires and maybe a few brake lines, ubolt the rack and pininon from the k member, leave the struts hooked up and unbolt the k member, the k member should swing down by the lower control arms and hang under the car, that should be enough room to ger the pan down.

now, do I put a stock pump in, or put a canton pan in?

if a stock pump is enough, and it should be, i'll go that route. what I don't understand is, lets say it is the pump sucking it dry, why did adding another quart of oil not make a difference?

It oil pressure does drop in every gear, not just first, but it's worse in 2nd, mainly I think for the reasons Lonnie mentioned. the car is in 2nd longer than 1st, and has a long pulling power band. But the thing is, it didn't do this the first 3 weeks i drove the car.

According to mellings website, they said it's not possible to suck a pan dry, even with a HV pump because of the metering system in the lifters, there would have to be 5 quarts of oil in the valve train, on top of the heads, and in the intake valley, and none in the pump, that I find hard to believe. But maybe I am wrong.

izzyz28

To clarify, my car also does this in first and second gear only, and sometimes just a little in third. The only reason I can think of is oil climbing up the back of the pan under acceleration. I can hold it at 5-6K in neutral for a year and the pressure will never drop. In fact, adding a quart just seems to make it worse. Same exact symptoms as the original poster. I'll probably just get the Canton pan and be done with it, especiall after I got hooked on autocrossing this past weekend. Let us know how it turns out.

LilJayV10

Well I put a stock pump in it, w/ a 3/4 inch pick up, problem solved. I guess it does suck the pan dry. Learn something everyday.