oil pressure

[dlrshort]

Hi, guys, I drove a '7l LT-1 today on test drive, the oil guage buried at 70 with little or no fluxuation. My '71 which runs fine has fluxuation depending upon accelleration between 35- 70. Is this ok?

Dave

 

[JohnZ]

Most likely some yo-yo put a "whizbang" high-pressure/high-volume oil pump in it (which it doesn't need), or the pressure relief valve is stuck shut; I've seen a stuck relief valve blow a filter housing right off the base.

 

[Radar]

Could be a bad gauge sender. If it really is 70 psig, that is way too high and could be trouble! Something is amiss with the pressure relief valve or there is a blockage in the main gallery, like a plugged oil filter, etc.

Radar

 

[dlrshort]

John/ Radar,

Are you saying the LT-1 is too high at 70 or my coupe which fluxuates?

Dave

 

[dlrshort]

John and Radar, as a side question, the LT-1, was cold and I only drove it for a short time. Would the oil pressure adjust or drop later?

Dave

 

[cntrhub]

Turn the engine on and off a few times. Watch the needle move. Did it peg to 70 at each start up? Did the needle stay pegged to 70 when the engine is turned off? Start the car. Let it idle. Is the pressure fluxuating like normal? It may have been a fluke, intermittent reading.
If this was a stuck ball in the oil pump, the crank seals would have failed and you would have oil dripping out both ends of the engine's crank.
Is the oil black and dirty? This can create a thicker and slower type of lubrication flow, which will cause increased oil pressure.

 

[Radar]

My 1989 L-98 runs about 55 psig on a cold start. It falls to about 43 at 2000 rpm and above when hot and 21 psig at idle. I suspect that 70 psig is abnormally high. Your (any engine for that fact) engine has an internal oil pressure regulating valve that should limit the pressure.

Question: are you running a super thick oil like SAE 50 or above? That may explain the high pressure. With typical oils like 5w-30 Mobil 1, I would think you should be around 50 psig or lower. I would get a shop manual and look up what the factory specifications are. They have those manuals at the library (like Chiltons or Motor Manual)

Good Luck
Radar :TALK

 

[Jack]

Could be a bad gauge sender.

No factory oil sender on 71 ... has has small tube (not wire) with factory mechanical oil gage.
JACK:gap

 

[Tom Bryant]

With a mechanical guage if the guage was on zero before starting and went to 70/pegged I would agree with John. We used to streatch the pressure relief springs in the oil pump to get a little more (or a lot more if you went too far) oil pressure. I realize that you haven't bought the car yet but a higher range mechanical guage temporarily connected under the hood would tell the story. If it's running a steady 80+ psi that's way too much for street use. I would be afraid of the tube blowing off the guage and ending up with several quarts of oil in my lap.

Tom

 

[dlrshort]

Tom, it was at around 70. I didn't drive it very long, it may be that it will drop after it's warm and thins out.

Dave

 

[jmp]

I doubt you have a problem, at least on the car the fluctuates. My 72 LT-1 does exactly the same thing (and so do many other people's cars -- search for this subject):

When I start up, the pressure is 70 and stays that way 'till the car gets warmish -- especially if the choke is on. Afterwards it drops to 20-30 at idle, and higher depending on my acceleration; it goes back up to 70 if I floor it. When the car is hot (but never above 210), the pressure still fluctuates with acceleration, but the range has shifted down: e.g. 20-60 or so. I've been told that oil pressure drops as the oil warms up.

 

[dlrshort]

Thanks, Joe, I'll let you know next time I drive it.

Dave