Farmall M missing on#2

Clint Evans · Nov 14, 2015

My M starts good and runs smooth for a few minutes then starts to
miss on number 2. Checked compression valves are good. New plug
new plug wire checked points on that cylinder correct. New ignition
coil. No water in oil no oil in water. Put it under load quits missing but
warm and at idle or fast idle will miss intermitantly. Sounds like it is
late firing or maybe exhaust valve is slow about closing?? Any
thoughts

DeltaRed · Nov 14, 2015

My Super got to doing that. Over time the valves got worn and 'tightened' up.After a valve adjustment,it once again runs smooth as glass....

rustred · Nov 14, 2015

the valve adjustment has to be the most overlooked operation. warm it up and adjust to .017. spark plugs cause intermitant misses. a valve miss u will hear in the exhaust pipe with a huff sound. a spark plug is just a dead miss.

MIKE FRENCH · Nov 14, 2015

check to see if manifold gasket is sucking air. Have had it cause miss like this in past several times

gene bender · Nov 14, 2015

Change that plug with one from another cycl see what happens.

gene bender · Nov 14, 2015

Mike remember that B i bought from you a few yrs ago. After getting the pushrods back so they worked and changing plugs it now starts and runs great never know just what you can find on thses old engines and how simple sometimes to get them running great.

Clint Evans · Nov 14, 2015

The plug swap mentioned I had already done. No difference I do agree with others it sounds like a valve miss. Reset clearances earlier and helped some. But miss is still there Again it shows up after about two minutes of running. Guessing the exhaust valve is warming up and starts to delay in closing. Like maybe some residue is causing the valve stem to be a little sticky. Maybe a week valve spring??? With valve cover off the valves look ok while running.

rhtx55 · Nov 14, 2015

Possibly a worn guide or crud built up on valve stem. Use diesel or marvel mystery oil, with the engine idling & valve cover off, squirt a abundant amount of either on each valve stem while running. Careful aim to get it on the actual valve stem of each above the top of the guides, through the tiny openings in the valve springs. Once the one causing the miss loosens up apply a abundant amount of "loosener" and then engine oil, keep at it.
Hopefully the gunk build up will be removed so oil can get back into the guide. If not, you will at least know which valve is sticking.

Janicholson · Nov 14, 2015

or the manifold is warping as it heats letting the intake get an air leak. Use an unlit propane torch with the nozzle removed to test all around the manifold. Jim

used red MN · Nov 14, 2015

I think you have a vacuum leak. Spray either or direct an unlit propane torch toward the gasket mating surface of the intake manifold to the head and around the intake runners. Do this while the engine is idling if the misfire goes away or there is a change in engine speed them you found your vacuum leak.

David G · Nov 15, 2015

I would think that it would miss on 1&2 if an intake leak because they share an intake runner, which would make me expect a compression of valve issue.

Did you check valve clearances, then compression.

Clint Evans · Nov 15, 2015

Yes. Still leaning to a slow exhaust valve. Tried spraying the valve stem and guide while it was running to help it . Better. So I will try that again tomorrow. Not sure the best cleaner to use. Back in the day use to pour transmission fluid in old vehicles to help unstuck valves. May try that as well

David G · Nov 15, 2015

Did you run compression check?

MIKE FRENCH · Nov 16, 2015

good deal, I have another B you need up here!

gene bender · Nov 17, 2015

Great sounds like you have found the problem

Farmall M missing on#2

Clint Evans

Member

DeltaRed

Well-known Member

rustred

Well-known Member

MIKE FRENCH

Member

gene bender

Well-known Member

gene bender

Well-known Member

Clint Evans

Member

rhtx55

Member

Janicholson

Well-known Member

used red MN

Well-known Member

David G

Well-known Member

Clint Evans

Member

David G

Well-known Member

MIKE FRENCH

Member

gene bender

Well-known Member

Similar threads