C-221 Intermediate Knock

Hey guys. So with all the snow and wind we just got,
I've been out plowing a lot. Sunday I noticed the
606 I've been using has developed a knock. Its only
there once engine is up to temperature, and only in
the 1200-1800 rpm range. Anything under or above
that and it sounds just fine. Had been starting and
running great prior to this...any ideas or where to
start?

On a side note, I don't know if it would be related
but I got the tractor stuck Sunday night. Had to
leave it sit out overnight until the neighbor could
come help me. That next morning I had a heck of a
time getting it started and once I did, it was
running rough. I got it back to the garage and shut
it down. Did some checking at that time, plugs were
wet and two were oily. I cleaned them, regaped and
put back in (has Autolite 386 now...thought about
swapping to 388). Also cleaned up the inside of
distributor cap and rotor as they didn't look the
best. Don't know if the rough running was from being
cold and having flooded it, or related to the
knock???
 
To be on the safe side, pull the pan and check to see if a rod bolt has loosen up. Have seen it a time or two. It was caught in time and no harm was done.
 
Where do you hear this KNOCKING , is it a lower end knock or is it mid way up in the block?? or is it a top end knock?? Bottom end like said below check the bottom end for a loose rod mid wya up then it could be a wrist pin bushing or just a piston looser in the bore then the rest or it could be a broken piston skirt. as for a top end knock then you may have something inbedded in the top of a piston If it is a wrist pin bushing they can run a long time with that . a broken piston skirt NOW i would start to worry as the rest of the piston could finish breaking and then you will end up with and inspection hole in the block that you really don't need. If it is a lower end failure here again it can get costly really fast, so a pan gskt will do two things either you will see what is wrong and be able to corret the easy problems or it will give you some piece of mind for the short term.
 
I think it sounded mid way up the block towards the front but I didn't spend much time listening. Its supposed to be warmer towards the end of the week so I'll pull the pan and look around. Anyone know what the main and rod bearing clearances as well as the rod and main bearing cap torques are? Might as well pull those and plastigage everything while I have it opened up. Thanks!!!
 
(quoted from post at 12:00:33 02/04/15) Looked at it last night...hope I can get the pan off without removing the wide front!
Before you tear into it, try using a section of garden hose for a stethoscope to help pinpoint where the sounds is coming from. It might save you a lot time in trying to figure this out.
 

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