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CarlC
03-27-2005, 05:53 PM
Since the engine rebuild and oil cooling upgrade last year there has been some strange oil pressure gauge fluctuations.

At idle, oil pressure is normal @ 40 psi.

At cruise, the oil pressure is centered around 55 psi @ 2100 RPM, but the needle flutters +/- 20 psi so fast that the needle is a blur.

Under coasting conditions, the needle fluctuations are less (+/- 10 psi), but still very apparent.

Here's a list of the before / after changes:

Changed the stock gauge feed plastic tube to a -3AN. The guage is a stock GM console gauge.
Oil pump from HVHP to Mellings 555
Elimination of the oil bypass to allow for CV Products oil filter adapter (no bypass)
Addition of lines and fittings for cooler (several unwanted, but needed 90*'s)
Addition of remote oil filter mount.
Addition of an in-radiator oil cooler.
Milodon 5 qt pan to CV Products 8-quart road racing pan
CV Products oil pan pickup.
Engine rebuild included new main and rod bearings.
10W-30 to Mobile 1 15W-50 synthetic.

The engine runs great, has no funny noises, and during oil changes there have been no abnormal particles.

Fatigue life of the gauge is a concern since I'd hate to have the gauge fail in the car. The other is if there is a high-frequency pulse in the system, what will it affect? Fatigue of the in-radiator cooler? Oil film thickness? etc.

Any ideas would be great.

Thanks.

camcojb
03-27-2005, 07:39 PM
First thing I would do is try another gauge. ALMOST impossible that it's fluctuating that much that fast.

Jody

chicane67
03-27-2005, 10:06 PM
Yup, my thoughts exactly.

It could however, be reversion from 90* fittings in the oil system. Air at the guage head...... or maybe just a bad guage in itself. I know when I went to liquid filled guages, all my needle problems went away, from what I would expect to have been a reversion harmonic in the transducer (guage/needle) itself.

Jim Nilsen
03-27-2005, 11:48 PM
Since it is a mechanical gauge it could have a leak/crack at a fitting or the hose and you are getting air in the line and causing spikes and drops as it comes and goes or you have what everyone else is saying, a bad gauge ! Just try a new hose and fittings to check. Poly hose is cheap compared to a new gauge for a test. I can't believe it's the new hose but you never know. The stock GM gauges are prone to messing up in all kinds of cars from that era. You used to always see the three cluster setup in any serious car back then for the obvious reason.

Goodluck , Jim Nilsen

CarlC
03-28-2005, 10:11 AM
New Autometer gauge is already on the way.

It was just interesting that it was working fine before the work, then started acting up immediately afterward.