Ford 8n Oil Pressure

[DerekF]

I got a Ford 8n few months back with a supposedly rebuilt engine within a year before I got it. I didn’t notice it had no oil pressure at the gauge until I had already brought it home. I did the ole “crack the line and see if oil comes out at the gauge” test. Oil came shooting out of the end and so I assumed it was the gauge. Bought a new gauge for it and finally installed it today. Still no oil pressure showing. So I looked it up. Supposedly air in the lines will cause it to show no pressure. So bled it until oil came out and then tightened the bolt and took it up to full throttle and still have no visible oil pressure… so what next?

 

[Roadworthy]

I don't know old Ford tractors so I don't know the expected pressure but I suspect it should be twenty to thirty pounds. Low oil pressure may be loose or worn bearings or the pressure relief spring. Too light an oil can also lower pressure. I suspect you should be running about a thirty weight oil. It is also possible the oil pump is defective. If the engine has been overhauled the pump may have never been primed. In older cars if I recall correctly, you could remove the distributor and spin a large screwdriver blade with an electric drill to get oil throughout the system before starting the engine. This would also create oil pressure without risking undue wear on the engine.

 

[John0829]

The Ford 8N is know (well know) for what we today think of as low oil pressure, fact is the old engines will run for YEARS with as little as 5 lbs. of pressure. As long as you show some pressure on the gauge at high idle you'll be fine. You can put 10W40 in it to make it show a bit more pressure if it makes you feel better.

 

[MiniDonkey22]

mine would run 5psi ish at idle when warm; I also remember that on slopes it would suddenly go to zero. Scared me a few times

 

[Texasmark]

What is the range of your gauge? Maybe its too high to read correctly. a 0-30# gauge is cheap and easily obtained that ought to give you a reading.
Not an N but years ago I bought a 4000 with no oil pressure (optimistically hoping it was the gauge or a clog in the line....bought it not running) where these engines easily run over 30#. In troubleshooting the mains were shot....glad I didn't pay much for it.

On oil pumps in general, I learned that there are basically 2 lubrication theories involved in engine design: One is low pressure, high flow, the other the opposite, high pressure low flow. On my Chevy trucks the oil pressure would follow the RPMs. On my Dodge, it would jump up to 30# at idle and stay there.

 

[jackl]

I’m sure you solved this sue by now, but the 8N has a pressure relief valve in the front of the engine above the crankshaft pulley. If the engine sits, sometimes the oil pump looses its prime and you have no oil pressure.

Take out the bolt and you will find a spring loaded rod. Attach a tube to a quart of oil, insert it in the hole and inject 5-6 oz. Replace the bolt, valve and spring. Start her up and see if that works as it should prime the pump.