Farmall 400

henryv11

Member
Has no compression on #3. PO said it started missing while running. Been sitting for long
time. We put oil in the cylinder made no difference. Both valves are operating and springs
seem OK. Could it be a bad valve or blown head gasket? I guess next step will be to remove
the head. Just wondered what you thought.
Thanks
 
You could pull the valve cover and check to see if all the valves are moving (pull the spark plugs, and have a helper turn it over). If any valve is not closing correctly, you'll find a significantly larger than normal (~.014) gap at the tappet. To fix it, you'll have to pull the head.

If it has a burned or bent valve, you'll have to pull the head.

If it has a blown head gasket, you'll have to pull the head.

If the piston rings have shattered and the cylinder walls are toast, you'll have to pull the head.

I love shortcuts just as much as anyone else, but in some cases, the best shortcut starts out by looking like the long way around. You may as well just pull the head and see what's going on.

HTH
 
So not to state the obvious but do both valves on that cylinder have some lash when in the closed position? If a valve is being held open that will also cause low compression. If the PO description is correct it sounds like it is most likely a burned/leaking valve. So ditto on what well worn says about "short cuts"
 
Thank you both for your reply's. Yes We did remove valve cover and determined that both
valves were operating and with some clearance. Did put my thumb over plug hole and not much
compression compared to the other cyl. Will remove the head and see what it looks like.
Worked on a few M.s first time for a 400. Will let you know what we find.
Thanks Henry
 

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