Help troubleshooting MH Pony engine problem

H everyone, I am hoping you guys can give me some direction on a problem I am having with a MH
Pony Tractor...

3-4 years ago problems started. When under load it would start smoking real bad out of the valve
cover breather. Anything more than driving on the level the engine would just shut down unless you
stopped. I did a compression check, don't have exact numbers, but if memory serves, three
cylinders were up around 105#, one was down around 85 or so. When I'd add a tablespoon or so of
oil to that cylinder pressure would come up....after that I was convinced it needed rings but at
the time I didn't have the time, so I drained the gas and put the tractor in storage. This is a
real nice original tractor so having the time to do it right is important to me, otherwise I could
have never let it sit so long!

Fast forward to a week ago....having heard good things about it, I got to wondering if using Lucas
HD Oil stabilizer would make a difference at all. I changed the oil, added 20% Lucas, also added
1/2 a bottle of Marvel Mystery Oil to the oil, and the other half Marvel to the gas tank with 2
1/2 gallons of fresh gas.

Tractor still starts hard....
-Once started though, it idles great.
-Even at full throttle if just sitting there it runs great....
-Getting a little bit of smoke out of the valve cover breather tube yet...although not quite as
bad as before I don't think.
No smoke or at least very, very little smoke out of the exhaust stack and I thought if it needed
rings I'd have exhaust smoke?
-When I first started it the tractor could barely pull itself up a very slight incline in my
drive...after 8-10 hours of running, it has gotten a little better, but clearly yet it can't
handle any kind of a load.

So what do you think? Stuck valve(s)? Needs rings in at least the one cylinder? Anything else I
should check? Might get time this weekend to take the valve cover off...anything else I should be
looking for?

I am also curious, if it is the rings, (and I wish it wasn't but I have a feeling it is?) on a MH
Pony, do you need to pull the engine or can they be replaced with the engine left in...

Thanks in advance for any help youcan offer...
 
Check the valve lash while you have the cover off, look everything over, springs, rockers, etc. Might look at the distributor, make sure the centrifugal advance is free and working, check the bushings for wear, look at the point setting and condition. Mark and play with the timing, you can put it back if it doesn't help. Look inside the air filter, not just the oil bowl, but up inside where the actual filter is.
 
Thank you for the tips guys, to be honest it surprises me, but that's ok. I just almost expected with that one low cylinder you guys would say it needs rings for sure...but I'll definately check everything mentioned here first...Thank you...
 
This Continental engine without a water pump when getting hot could just need new rings as they can loose the tension to the cylinder walls when getting hot. If the engine is up to spec every where else and just got hot new rings could be installed from the bottom end without removing the head. A lot of ifs goes into this when you have years of history on the engine. The only real way to know for sure is to check for wear at every wear point by tearing it down.
 

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