popo8

Since I'm pretty new to the LT1 world, maybe some of you who are more familiar with them can give me some input to let me know if I should worry. I have a 1996 Z28 with around 130K on it. The motor has never been apart, so it is all stock. When I first bought the car and it had petrolium based oil in it, I would notice the oil pressure drop at idle, altho it would be high when the motor would still be cold... If I let the car idle long enough I would notice the "check guages" light come on, and the oil pressure needle would be in the red... although the motor would not be making any "bad" noises. Using a little "shade-tree" techniques.. I switched over to a synthetic, heavy weight oil (mobil 1), and added Lucas stabilizer with every oil change... It no longer drops into the red after long periods of idle, but it gets damn close...
-Some people have told me that LT1's are ment to idle at about 6lbs of oil pressure, and that is roughly what it would be above the red... but others have told me that LT1's with alot of mileage have a tendency of chewing up the main bearings..... Which is true??? or are they both right???? Should I be concerned? By the way when I drive, oil pressure is great......

Z28_95RIDE

6 pounds is the low service limit at idle but your gauge (oil pressure sending unit) may not be accurate. 130k can be a lot of miles if the car did not have regular oil changes. Otherwise, the LT1 crank and rod bearings should be good for 200k with reasonable use, or so I have been told. Different oil filters will cause some changes in oil pressure readings.

shoebox

Sometimes old pressure sending units can show lower pressures when they get hot. Try changing the unit.

popo8

Do you know which oil filter I should go with to show higher oil pressure??? I just replaced the oil sending unit, a few months ago, when I replaced the oilpan (with OEM) and the Kmember.

klpps

I have the EXACT same problem. I switched over to a thicker oil and it keeps the low oil light from going on, but it still gets pretty close. When its cold I have normal pressure but as it gets hotter the pressure drops, and increases as I accelerate. I have a mechanical gauge and I know its not the sender or the sensor. I was told it was a cam bearing. I've driven it like this for years and the car still runs good. Let me know if you figure out what the deal is.

RICEFEDZ28

I had that problem. The pick up tube fell off the oil pump and took out the bearing. Drain your oil and knock on the oil pan. If the tube fell off it will bounce on bottom of pan.

popo8

I dont think the pickup tube fell off. Because I just put a new OEM pan on the car when I installed the tubular kmember, and the old one was in tact... I replaced the sending unit since I was in there, and the oile pressure is identical to previous...

popo8

Ok.. I'm glad its not just me... and I will keep u updated if I learn anything. When u put the mechanical guage on ... was the pressure still as you explained it above, or was it more accurate????

camaro81

fyi, mine has 125k miles and idles between 15-20psi

It does seem low, but the car runs and sounds great and still hauls ***. It still bothers me a bit when I get out of my trans am that idles at 50psi and watching the oil pressure on the z28 drop to 15 :/

LT1's hold up great if treated right though, if its not knocking I wouldn't worry about it.

klpps

The mechanical guage read the same. You and I have the exact same problem. I am replacing my oil pump with a high volume pump in a few weeks. I'll check to see if the pick up fell off, and if it did, i may keep my stock oil pump in.

popo8

I'm concerned , but not worried... but I do worry when Im jumping on it hard and watching it get into those upper rpms... Im afraid it will come apart, or start making that lovely knocking noise.... Once I get axels and gears,I want to take it back to the track, since the last time i ran with street tires, and only got a 17sec pass after cooking the first two gears....then grenading the clutch....

popo8

cool... keep me posted. PLEASE.

Z28_95RIDE

Sorry, no. I'm just passing on what seems to be reliable information. There are a lot of threads on oil filters that can be searched. My favorites are wix, napa gold, k&n and mobil 1. I don't think you will see a big change from the filter but some have reported an improvement. I'm under the impression that only a small percentage of the oil passes directly through a filter as the entire volume moves. In other words, the oil is filtered by redundant trips to the filter and eventually every drop, by shear statistics will find its way to being filtered. What I'm saying is the oil filter isn't the bottleneck one might think.

While the subject is alive, here are few other tidbits I have encountered. A faulty PCV valve can exacerbate a low pressure reading. One member changed his out and gained 5lbs of pressure. I tried this but didn't gain anything. Still, it was worth the few dollars and minutes.

The culprit of low oil pressure is worn cam bearings as someone else already pointed out. That is why there is no low end knock with marginal pressure. The rod bearings are still within service limits.

A high volume oil pump can result in destruction of the pump's composite drive gear. It was not designed for the increased load. I spoke with someone locally that didn't like the low pressure reading at idle and went with an hv pump. The drive gear disintegrated at wot which ended the motor. I have read about this happening more than once.

popo8

Thanks... I guess I will try some different filters, these next few oil changes and I will see.

madcat

I've had this problem since I bought my car. Right now I've switched from Mobil1 0w40 to 5w30, the filter I use is a K&N Oil Filter HP-2002... Right now my car is running better on the 5w30, but even with this problem I've been to the track about 4 times, plus everyonce in a while I open her up on the highway. But I'm sitting a little over 135k miles and I haven't been able to figure out what causes my oil pressure to drop once the car warms up. One thing I have noticed I didn't see posted here, is that if I get on the breaks quick at a stop the Oil pressure gauge will bottom out and my check instruments light will come on. I've been told though that the engine just needs a good rebuild, but haven't had the cash to do it yet. I do plan on subscibing to this thread to see anyone figures out a fix for this problem. O' and if any of you live in the Norman, Oklahoma area and wanta look at it just msg me.