farmall 100 oil...top end

Fri Mar 29, 2013 7:22 pm

Hello,
I was having the oil pressure drop off after the tractor would heat up.i read on these forums about the oil pump cover warping and the gasket giving up between bolt holes. This is exactly what i found when i got into it. I lapped the back of the cover and put a new gasket in, now it has great pressure even at idle. Thanks again for great advice off this forum!
Next issue. The reason i was concerned about the oil pressure is that it didn.t look like i was getting oil to the top end how i would like. It has the welded rocker arms. One of them is allowing oil out of the top and it.s running down the little groove like it should. The others are getting oil along the central shaft because there is oil underneath each arm on the shaft but it doesn.t come up through to lube the contact points on the ends of the arms.
My thought is that since the pressure has been low for a long time maybe this is gunked up on top? Now i have great pressure all the time just no oil out those little holes on top.
What should i do?

Re: farmall 100 oil...top end

Fri Mar 29, 2013 7:41 pm

The rocker arm shaft is supported by 3 brackets. The middle one is held by a short stud with a nut. The stud is hollow, open on the bottom and out the side. All oil to the rocker assembly goes through this stud. It is a pretty small passage and seems a likely place for a restriction, if there is one. I would suggest checking it. Be careful tightening the nut on that stud. It is easy to twist off.

Re: farmall 100 oil...top end

Fri Mar 29, 2013 10:14 pm

Thanks Jim,
I will check that as soon as i get some good allthread to replace the valve cover studs. Seems sometime since 1955 these ones got bent slightly and the rocker arm assembly doesn.t want to come off... I'll just replace them when i check the middle stud. Thanks for the reply. Will update when i have news.

Re: farmall 100 oil...top end

Tue May 21, 2013 3:46 pm

Hello,
Jim, I pulled the whole assembly off and checked the stud. It was clear but just to be sure I blew some air down it as I had read that in another forum. I disassembled the rocker arm assembly and soaked everything in kero. There are these little squiggly "lines" scratched into the hollow "bar" that the rocker arms rotate on, by the looks of it these are to provide clearance for oil to come through. The arms that still had some of these "lines" or channels would oil better than the others but I talked to an old timer farmall owner out here and he said those are usually long gone by now and that it should still oil without them. SO I soaked the "bar" that is pressurized with oil and blew it out good. Put everything back together installed and let her rip. It oil's great now.

Re: farmall 100 oil...top end

Wed May 22, 2013 12:40 pm

Good deal! Probably saved yourself a bundle of $$$ by taking care of those two fixes. Surely they were accelerating engine wear and pushing you toward a premature rebuild.

Re: farmall 100 oil...top end

Mon Jul 08, 2013 2:53 pm

I am curious as to what the correct oil pressure on a Farmall 100 should be. My pressure starts off at about halfway up the dial (it goes to 75 psi) but then it drops down to the lowest mark -- which I suppose is no more than about 10-15 psi.
Otherwise it is running fine over a full day.

Re: farmall 100 oil...top end

Wed Jul 17, 2013 12:49 pm

If you have a harbor freight store nearby, they have a nice, inexpensive oil pressure test gauge kit that will show you accurately what your oil pressure is. It screws right in place of the stock oil pressure gauge, and has a calibrated dial.

10-15 is on the low side for a 100.

I think you can drop the oil pan and remove the oil pump on these engines. Once you do that you can pull the cover off the pump and true it up on a piece of glass with some wet/dry sandpaper.