Farmall M Running on Two Cylinders

Our M started running on only two cylinders the other week. It has the kerosene head on it and has 88 psi of pressure in each cylinder except cylinder 3, which has 62 psi. I decided to determine where the leakage was coming from, so I got a tube and filled the cylinders with 50 psi of compressed air with each cylinder at TDC. Each cylinder leaked pressure through the intake valves, as you could hear it "burping" into the oil bath. Cylinder 3 also had a substantial leak from the exhaust valve. What was odd though was that I also heard a LOT of air moving in the area where the pushrods are located in the head on all 4 cylinders. It sounded below the top of the head, but above the mechanical lifters. You could feel the air moving if you held your hand over the area. At first I thought that it was blow-by past the rings, but if I opened up the oil level check petcocks, no pressure came out, the noise stayed the same, and there was no movement of air out of the crankcase breather. What else could cause such a noise in that location? It seems unlikely that it would blow the head gasket out on all 4 cylinders into the pushrod gallery when the water passage is directly in front of it and the radiator showed no bubbles during testing. Any ideas?

You are correct that the air you feel is blow-by. The oil passages in the cylinder head are larger than the petcock so leaking air will easily escape upward.
I have a cylinder leak-down tester that has a gauge reading percent of air loss and you listen or feel for air escaping to determine what part or parts are worn/damaged.
Sounds like your engine needs an overhaul!

I use a shop vac with a peice of paper over each intake/exhaust port instead of compressed air. use lapping compound to seal the valves but you will soon need an overhaul, just do it, this site is so helpfull

Check the location of the wires on the distributor and the direction it rotates. Some 4 cyclinder engines will run (My W-30 did!) if you have the wires going the wrong way (Clockwise vs Counter-Clockwise or vice-versa). Two cyclinders are timed correctly and two cyclinders are firing when the intake valve is opening.

Running on two cylinders? Doesn't that make it a John Deere?

I'm sorry, I know it's not funny, but I couldn't resist!


Gene