Originally posted by Charlie McCall:
Originally posted by george pence:
If the reading is bogus (most likely) then something is creating a short circuit, as increased resistance, a bad connection or wire, would create a lower reading. The things to check for are: oily or greasy pressure sender; the wire connected to the pressure sender possibly grounding out on the case of the pressure sender; a wire connected to the back of the gage shorting out.
Your friend on the DTBB
I recently installed a mechanical pressure gauge because I didn't like the flaky readings I was getting. I couldn't find any pattern to the different readings - it wasn't electrical, because the readings weren't related to having lights on, etc. It wasn't engine load related, because sometimes the pressure would surge or dip on a flat stretch. I replaced the sending unit, cleaned all the connections, and still got weird readings.
I installed a mechanical gauge and got a rock-steady oil pressure of roughly 60psi at highway speeds with everything warm. Sometimes my stock gauge would read as high as 50 or so, or as low as 30. But the mechanical gauge didn't waver.
What's really happening? The only way to tell is to put a mechanical gauge on and compare numbers. Are you being paranoid? Dunno. Most engines give you advance notice before digesting internal parts, and fluctuating oil pressure could be a sign of something getting ready to let go. Or could be a bad gauge.
Before installing the mechanical gauge I decided to change the oil, change the filter, and then just drive it. If the engine was going to die, then it was going to die and there wasn't anything I could do to prevent it. But the gauge gave me peace of mind...
It isn't unusual to get inconsistent readings with an electrical gauge.
I don't personally like the Ford sender with the Italian gauge.
The oil pressure readings on a new engine on the stand will always give me 100# readings with a mechanical gauge.
As soon as you drop the engine in and fire it up it will show 60-80 on the electrical gauge.
There are all sorts of complications with this set up.
For one you can be getting voltage variations to the system and thus false readings.
You should have a voltmeter in the car and be sure that you are getting readings on the hidg side (15v) rather then the low side (13). That alone will drop the gauge readings.
Also depending on what oil you are running, multiviscosity oils will vary both your high (cold) and your low (hot) readings.
One oil will give you 20 # hot at idle and the other will be 35#s.
Actually most of the Ford FE's will give about 15-20 hot at idle and that is ok.
The Cleveland isn't any different then any other engine in what pressure it needs.
It's more important as the volume it gets and where and at what loading.
A restricted oil lifter gallery with solid lifters in a Cleveland will keep more oil down low where it belongs rather then pumping it all up into the covers for the juice lifters like these engines do.
I've seen them hold two inches of oil in the valve covers under "normal" operating conditions.
The valve springs like that in NASCAR but you don't want that on the street.
You can test your engine for pressure variations after installing a solid grade of oil such as a strait 40 weight.
If the fluctuations are reduced with this oil then the oil that you are using is a major player in the pressure.
I know that after making a pass at the drag strip the 100# reading you had at the line is going to be about 15# when you come back.
That's because the engine just killed the viscosity of the oil.