Oil Pressure Gauge Reading

Just curious, what actual psi's are represented by our stock gauges? We have the H then the "in-between the lines area" and then the L.  What psi's do those marks represent?

Hey, even if they had a value associated with them I wouldn't trust the accuracy.

Back in 2003 when I rebuilt my 73 H code, I hooked up a mech oil pressure gauge at the engine in-line with the factory pressure switch. At the time I had 5-30W dino-oil (for the 1st 2000mi, then switched to Synthetic). Just wanted to see what factory gauge really represented.

Cold initial startup (choke on - 1400 rpm) was 75 psi - factory was 7/8's towards the H. Engine warmed up (choke off - 625 rpm) was 35-ish +/- psi and factory reading was 1/3 past the L. Driving at 50mph (approx 2000 rpm) was 45 - 50 psi - and factory gauge was just a bit under the halfway point on the line between the L and H.

i was wondering the same thing as JD. even if the pressure is kinda/sorta in that area i'm happy.. since i rebuilt the engine this spring mine runs around 3/4 almost all the time. depends on cold or hot i'd say 5/8 to 7/8 of gage at idle. running down the road hot it's like 3/4 gage..

I've been cursory towards the factory 3-guage unit since the first day I bought the car. The Temp seems appropriate when compared to a thermometer in the radiator, on my car, the temp "arc line" starts at 160 degrees, again, seems right. BUT....that oil pressure unit is a guessing game at best, and when compared to my auxillary guage, it's way off, indicating Low when the SW mechanical oil guage shows 40 hot idling and almost to the middle from low when the mechanical guage shows 70 psi at rpm, for which I would call 70 psi "high" ( I run a high volume oil pump with a shimmed pressure relief spring for those pressures). The Alt guage has never moved, or indicated anything, I had it checked when I first bought the car, and the mechanics shop said it was in fine working order, but I've never known if it was to indicate amps, or volts.

I've seen some guys replace the center three gauges with Autometer gauges that have black faces with orange/red pointers so they look like the factory gauges. I hate to go hacking up my dash wire harness for that swap, let alone the amount of time to make the adaptors to hold the Autometer gauges against the back of the plastic facia.

I wonder if someone like that Bob's Classic Cougar Innovations could re-build, re-calibrate, and add Temp/psi numbers to those gauges....I know he re-builds the Alt guage to read Volts for customers.

None of this really matters until the engine starts to smoke.

If the dipstick indicates "full" you should be good to go.

Same thing with radiator, at the full mark no problem.

mike

Ammeter gauge is notoriously difficult to move. With engine off, headlights on, brakes on, door open, and cigarette lighter on, you might get a half needle's deflection.

The rest of the gauges are best described as indication gauges and are uncalibrated and cannot be calibrated. When normal, note their position; when they move away from the normal position is when you are about to have problems. These gauges all rely upon resistances in the sending units, the wires, connectors, and voltage from the constant voltage regulator (except the ammeter). There simply is too much slop to calibrate them.

I suspected I had an oil control issue at the top end of the strip on my 429 as I thought I heard the lifters getting noisy in the last 30 yards. However the stock oil pressure gauge never moved as it is slow to respond. I fitted an aftermarket gauge and I was right - I lose pressure at the top of 3rd right before I shift into 4th. It recovers then because the oil can drain back into the sump. The pressure then starts to dip again in 4th right before I cross the line at 98mph. So obviously the mechanical gauge is a lot better at telling you what is really going on. I have it in a pod on top of the dash with an AFR gauge & vacuum gauge for tuning.

     I've seen some guys replace the center three gauges with Autometer gauges that have black faces with orange/red pointers so they look like the factory gauges. I hate to go hacking up my dash wire harness for that swap, let alone the amount of time to make the adaptors to hold the Autometer gauges against the back of the plastic facia.

   I wonder if someone like that Bob's Classic Cougar Innovations could re-build, re-calibrate, and add Temp/psi numbers to those gauges....I know he re-builds the Alt guage to read Volts for customers.

Click to expand...

 Spike I'm sure you read the post I put up a few months ago, " looking to upgrade factory Center Gauges" If you dig through that, I (think I) included picture of my proposed conversion. I used Bocsh mechanical gauges as they are down sweep and look even more like the originals. The bracket I made will work very well, but a bit tricky to make if you're not that way inclined and unfortunately I can't supply the bracket as I no longer have shop access. (I finally RETIRED FOR GOOD!!) I may be able to supply a sketch if that helps. PM me if needed. ** Look at page 2 of this post**

There have been several post on this if you and others care to search.

 At this time I have not installed the center panel I made up as I really don't know if I want to cut a 1" hole in the original unmolested firewall to get the sending units through.

Geoff.