Oil pressure

[rasouth]

Just a quick question... What should my oil pressure be at? At start up I am reading 35-38 but after driving it drops down to around 15. I checked level of oil and it was fine but when I looked into cam housing it was dry. I disconnected coil wire and cranked engine and after several revolutions oil started oozing up to crankshafts.

[narfire]

I have a line conected to the oil filter housing to an oil pres. gauge and at idle cold I'm around 60 pounds, and once warmed up and then settles down , the pres. is around 45-50 at idle and at 100 kms/hr and 3200 rpm or so, pres. is around 50-60 pounds. I currently have Castrol 20/50 in the engine

[beachboy]

Chris, your using a little thicker oil, so you should have a little more pressure than normal.
Usually 40 is normal when warm, though these gauges can be a little suspect at times.

Rasouth, You could have a dented oil pan where the pickup is located, or a worn out oil pump. What oil are you running in there now? What is the viscosity?

[mdrburchette]

Make sure you're reading the oil pressure with a mechanical oil pressure gauge to get the true readings. The oil senders on our cars get lazy over time and won't read the true pressure.

[rasouth]

I, too, installed a mechanical oil pressure gauge to the filter housing a while back because I had some clacking/knocking noises and wanted to know what my pressure was. I switched out my oil to 40 wt. but that made no difference in the noise. I removed the oil pan last night and removed the pump. There was a little sludge in the bottom that might have clogged the pump but the pump screen looked clean. I hooked my drill to the pump, stuck the pump into a bucket of oil and started my drill. Oil gushed out leading me to believe that the pump is working good.

[mdrburchette]

So, the oil pressure readings you posted are from a mechanical gauge?

[rasouth]

The gauge is mechanical. I just finshed putting the oil pan back on and refilled with 20/50. The pressure came up a bit to around 43, but after driving for a while pressure went down to around 27. I looked into the camshaft and the oil seemed a little low as if the oil isn't being pumped into the cams once the engine warms up.

[beachboy]

Although your oil pump is pumping oil, I think it is worn out and not producing the pressure you need. The fact that as the oil warms up, the pressure goes down is a clue. Also, running 20/50 and only getting 43 at start seems too low. Like Chris says, his is around 60 psi.

[So Cal Mark]

pressure is created by the restriction of forcing oil through the crankshaft bearings. If the lower end is worn, low oil pressure. The pump could be worn as pointed out, and there are specs for clearances once the pump is disassembled

[rasouth]

While I had the pump out I checked the specs and every one was within range. I checked the housing for damage and did not see any. My oil pan is a little wrinkled but not dented and I do not believe the wrinkles are bad enough to effect the pump.

[DUCeditor]

When I first got my `77, back in `88, I was concerned about the low oil pressure readings. My mechanic, who learned his trade in Italy and who really knew Fiats, said "if it were really that low the car wouldn't have lasted this long." That was 22 years ago. The gauge still reads the same now as it did then. He told me that was typical.

The reason the gauge reads lower after the engine warms up is that the viscosity of the oil is lower then.

One thing that helps is to use that old standby from when these cars were new: STP. This honey like goop likely doesn't work any of the miracles the advertising of that era promised ("Stops oil burning" "Makes you engine run like new") but it DOES raise the viscosity to raise the oil pressure a bit and my car loses (Leaks? Burns?) less with it in than without it.

Oh, and speaking of `70 era cures, I also find that the additives sold back then (and still available now but no longer needed on nerwer cars) that is designed to swell worn gaskets and prevent leaks, works, albeit not perfectly. Again, I find that if I add it the oil seepage greatly slows after a couple of days.

Old cars. Old ways. What can I say?

-don