Ok guys... i'm about to consider dropping my oil pan and swapping oil pumps to a high pressure one (oh, what a joy that would be). This oil pressure is really starting to worry me. When I bought all my parts, i went with what you guys said to do and I got a stock oil pump. My kit at first had a high volume (i think).

It's 90 degrees outside right now. I just got back from returning the Lucas Engine Oil and Transmission Treatment products.

A/C on, in gear... the car hesitates when i first hit the gas, and the tach is showing around 600rpm ( :confused: ). A/C off in gear, idle is fine and no hesitation (so i think that is a programming issue) With the A/C on at idle in gear the oil pressure is JUST above the solid area on the guage. At 45mph in 4th gear (OverDrive), it's around 22psi. That's about 1400rpm or so. if i give it gas and rpm's go to 2k+ then pressure is around 40 (or higher for higher rpms).

I just put a poopie load of money into this engine at the beginning of this year and I don't want to have to buy a new engine when my bearing get too hot from lack of oil.

Oil temp is around 230 when oil pressure is down low... and this isn't NEAR how hot it's going to get in July. at least 10 degrees hotter.

What do i do???

edit : fixed the low idle with A/C on. Had to adjust the TB blade screw because the IAC valve was maxed out.


[Modified by Glock'94, 2:02 AM 6/5/2002]


[Modified by Glock'94, 2:03 AM 6/5/2002]

 

Glock,

I am no mechanic, but is there a way to attach a guage to the engine to check the pressure, and see if perhaps the guage is reading wrong???

Just a thought
Gonzo

 

I've replaced it already. I bought a manual guage I'm going to try, but i doubt it's going to show any different.

 

I don't claim to be an expert. But let me give you my understanding of the issue based on my many years of engine repair experience.

First of all, Hi volume and Hi pressure are two different ways to measure oil. A high pressure pump maintains hi pressure and does not necessarily mean that if flows hi volume. Your engine determines the ability of how much volume of oil can be moved at a specific time based on the amount of pressure that the pump puts out. A higher pressure pump would move more oil thru the engine than the same pump with a lower pressure pump setting at the rpm it was specified for. This is why some have taken the stock pump and shimmed the spring in the pump to improve the oil pressure. A high volume pump may move more oil at a lower rpm. However, at a higher rpm, a great amount of that oil may be bypassed back in to the oil pan because your engine cannot accept that amount of flow. The oil pressure valve will bypass the excess oil as the max oil pressure is achieved. A high volume oil pump also takes more power to pump so that more horsepower will be lost to achieve the duty of moving more oil. If the size of your oil passages are increased to give better oiling capacities, then a high volume pump is in order. If it is stock in oiling capabilites, then a higher pressure pump that is rated at stock volume ratings would be better. The only exception that I can imagine is if the motor requred alot of oiling at low rpms, then a high volume pump could provide more oil at the expense of some horsepower loss at high rpms.More oil volume does translate to better distribution of heat and aids in cooling certain areas more effectively. I hope that this helps to understand which is better, hi volume or hi pressure. This all is affected also by oil temperature and the ability of oil to flow base on oil weight ratings and operating temperature. These variables are things that affect the basic theory above. You are correct though to beleive that more oil pressure at idle will help to prolong the life of your motor. However, one key is to avoid prolonged idle times if possible especially at extreme temperatures. Improving your cooling system could prolong the life of your motor if your engine experiences extreme oil temperatures since it also helps to cool the oil in the system.

Good luck and keep that motor running healthy!
:cheers:

 

Thanks sharky! My engine was built with looser tollerances, so that's most likely why the pressure is lower.

My guess is that the lower pressure I'm seeing is due to more volume of oil being allowed to go through (make sense?). So would changing to a high pressure be something you see as a wise idea?

 

Glock...

I think your sweating it too much!

If I recall your engine looked like tar inside before you redid it, Right?

Well that stuff was everywhere not just in the upper end. I mean it was around all your bearings, lifters, etc. I bet your OP was always ~50 or so before right? Well that is because of all that crap sealing all the oil location. That is much worse, because 1/2 of them probably were not getting oil at times.

Now with your engine in a *clean* state. It is doing exactly what it is suppose to.

My car has done exactly what your is doing from day one. When I redid my upper half of the motor it appeared all that was done to the engine was taking a new block, putting some oil in it, drainging the pan and tearing it back apart. In other words it was about as clean as you could get.

A friend at my parents dealership had a vette and we pulled the valve covers to adjust the RR and his looked exactly the way yours did. Guess what his OP was always at 50-60PSI at idle, cuise and WOT. He always ripped on me when he saw my oil fluctuating, saying that is not right.

After I took mine apart and he saw the way mine looked in comparison, he put his up for sale, figuring something bad was going to happen to it soon. He was probably smart in doing so.

I guess I am just trying to make you aware that it is probably fine your just not used to it being the way it should be.

Remember my TC problem I had, well with it working the way it should now, and with the added stall speed. If I didn't know better I would swear the tranny was slipping.

just my .02


:cheers:

 

yup

nope, oil pressure was actually just a little higher than it is now


hopefully

My car has done exactly what your is doing from day one. When I redid my upper half of the motor it appeared all that was done to the engine was taking a new block, putting some oil in it, drainging the pan and tearing it back apart. In other words it was about as clean as you could get.

A friend at my parents dealership had a vette and we pulled the valve covers to adjust the RR and his looked exactly the way yours did. Guess what his OP was always at 50-60PSI at idle, cuise and WOT. He always ripped on me when he saw my oil fluctuating, saying that is not right.

After I took mine apart and he saw the way mine looked in comparison, he put his up for sale, figuring something bad was going to happen to it soon. He was probably smart in doing so.

I guess I am just trying to make you aware that it is probably fine your just not used to it being the way it should be.

Remember my TC problem I had, well with it working the way it should now, and with the added stall speed. If I didn't know better I would swear the tranny was slipping.

just my .02


:cheers: [/QUOTE]


[Modified by Glock'94, 7:04 PM 5/31/2002]


[Modified by Glock'94, 7:04 PM 5/31/2002]

 

With oil pressure too low, the computer will shutoff the engine, right?

 

even "loose" tolerances shouldn't flow that much oil. i've never seen a well-built engine that flowed too much for a stock oil pump. even a friend's 1000+rwhp mustang had enough oil pressure with a stock pump and .003" clearances.

most of the times a HV pump flows so much that the bypass can't keep up, so the pressure goes way over the bypass spring's setting. so if you pop a HV pump in there and only see a max of 60-70psi, you still might be covering up a problem, since you have no way of telling how far the bypass is open at that rpm/pressure.

do you have an oil cooler which might be clogged?

something wrong with the filter?

lastly, you might have a new sending unit, but maybe the gauge in the dash is messed up. (unlikely, though.)

i've seen symptoms very similar to what you describe. three times. twice it turned out to be the oil pump's bypass being stuck partially open. the 3rd time was an oil plug in the block having vacated its spot.

once i saw a pump where the bypass stuck closed. that deformed an HP series fram enough to unseat the gasket. it blew a regular filter wide open within .2 seconds of a running engine. pretty cool to watch...

 

8000 miles on my engine. 1200 RPM at cruise was 24 psi, 50PSI under load. Idle dropped to 10PSI shortly after I noticed the low cruise pressure.

2 weeks later, the pressure went to 5 at idle.

Pulled the bottom end. Rod bearings 5,6,7 and 8 are all badly worn. Rear main and second to rear main are shot too. #8 exhaust cam lobe totally gone (non-roller).

I had had the pickup screen smash off when I bent the oil pan, but fixed that withing 20 miles. In fact, it broke the tack weld on a couple of occasions. That could explain it for me.

Now ask yourself, do you want to be as dumb as me and let it go to see how low you can go ;)

Good luck, -Matt-

 

Yes, maybe you have a looser engine. But anything close to 10 psi at idle would be dangerous. I don't feel comfortable at anything below 20 psi. However, I have seen many loose ones at 15 that ran fine for years. I did not see where you indicated what it was at idle during that 230 degree incident. But if you put in a higher pressure pump that has stock volume ratings, you will not have achieved anything since the pump would only limit the high pressure side of the scale. If your engine is really loose and that is the best guess at what it is, then get a high volume pump. That would be the only thing that could save your engine by giving more oil to lubricate and cool the bearings. But that is not the best soultion to the problem. Perhaps you already have a problem somewhere else that is eventually going to cause a bigger problem. Maybe you have bearings that are already gone and that they just have not failed. This could explain the loss of engine pressure. Remember that any loss of restriction by extreme bearing surface tolerances could explain the loss of engine pressure.

First, you need to verify the correct engine oil pressure by using a mechanical guage at the engine block. You can then go from there. I had a fellow mechanic that had problem recently with an engine that had low oil pressure at idle. It seems that some engines use a valve in the oil filter that helps retain pressure in the engine. When the engine is off, this valve attempts to maintain pressure to some degree in the engine and keeps the engine from starting with no oil in the passageways. Well, somehow, this mistake of using the wrong oil filter, one without the valve, caused the engine to lose oil pressure at idle. A quick change of filters solved the problem.

:cheers:

 

pressure was just above the solid area (i think the highest point of the solid area is 8psi). My guess was 10psi or so.


[Modified by Glock'94, 7:55 PM 5/31/2002]

 

i just remembered something else that happened to a friend, with a rebuilt LT1...

apparently, it's a fairly common thing for a tolerance mismatch between the oil pump driver and the block. part of the driver shaft (and by "driver" i mean the mechanism that takes the place of the distributor in order to spin the oil pump) is located by a close tolerance bore. this bore is force-fed oil. when the shaft is too loose in the bore, mucho oil spurts out.

the scenario for my friend was brand new rebuild, and once warmed up, idle oil pressure was ~5psi. after wasting time pulling the pan, checking bearings, he found out it just needed a new pump driver. problem instantly solved.

just something to think about, as i remember he said he'd found out from some builders that this was common.

 

Now this is very interesting. Can you give a more thorough description of where this oil pump driver is? Is it just the bar that attaches to the cam with a gear, and goes down the shaft at the back of the block into the oil pump to make i spin? (i always thought that was called the oil pump drive shaft). :confused:


[Modified by Glock'94, 12:31 PM 6/1/2002]

 

I was looking through some diagrams in my service manual and it looks like the oil pump drive shaft can only be replaced by dropping the pan and oil pump. Anyone know if it's possible to do it from the top of the engine?

I know that you prime the oil system from the top with a drill but I'm not sure if that "oil driver" can be replaced there.

 

on the lt1/lt4, the pump driver takes the place of the distributor, as a means to spin the pump drive shaft. it's true that the drive shaft can only be replaced by removing the oil pump, but it's not the drive shaft that's in question.

it's the assembly with the gear that you mention. you'd only need to pull off the intake in order to change it.

 

Ok, i'm gonna need some more convincing that this is the problem before i rip into my newly built engine. Anyone else heard of this???

 

I have heard of this. But usually an engine oil pressure test is performed during a rebuild with the manifold off to observe for any leaks. If there is an issue with mating surfaces and oil leaking enough to significantly reduce oil pressure, you should catch it during this process. I can not say that I have seen it happen. But it may be a cheap way to check and verify that it is not the problem. It would be easier than disassembling the motor to check for tolerances. :seeya

 

Glock, before you do anything, hook up your mechanical gage and verify your pressure. Even if you wire tie the thing in your engine compartment.

I have a mechanical gage in my truck and still have the original thing still hooked up in the dash. I get a good laugh at the stock gage readings when I’m bored.

If you verify the readings, then you have to start digging. I would start by talking to the people that did the machine work on your engine.

 

Like alot of us have said, check the actual pressure at the block by using a mechanical gauge. DO this before you continue to lose sleep over the matter.