pig in a poke - where to check for cracks?

OK so I brought home a 2N last weekend - motor was locked, I offered a quarter of what they were asking and brought it home. I dumped ATF into the cyls and noticed 2 plugs were black and 2 were rusty. Every time I've walked by it this week I've left in in 3rd and rocked it back and forth in the hopes of breaking the motor loose.

Yesterday I noticed that the exhaust pipe has a split at the J-Bend..... I'm thinking it was full of water and froze.

The tractor has the through the hood stack for the aircleaner and there was no cap over it, the sediment bowl at the bottom of the aircleaner is missing and so is the tube to the carb.

I think this thing sat out and collected rain over the years until the aircleaner was full, water ran down the tube, through the carb and filled one or two cyls in the motor until water ran out the exhaust.

Cyls 2 & 3 had the rusty plugs. I'm thinking that to free up the motor the head's going to have to come off. I don't see any cracks in the manifold, I haven't opened the carb yet.

Anyone got any things I should look for besides stuck/rusted valves, or split liners? There's no water in the oil on the dipstick but I should probably drain it to be sure.....

Crack the crankcase drain plug and see if any water runs out.

You may have lucked out since the water would have to go up hill into the intake from the carb. And the exhaust may have split before any water backed up into the exhaust manifold/engine.

Rocking a tire like that is sort of like trying to pull your pick up truck 100 yard by your self it might be able to be done but not likely. Set a 12 volt battery on it and use short fast taps on the starter button. Have the plugs out when you do that. If it is going to pop free it will that way. I do it ALL the time and have yet to hurt any thing but a push rod and that engine does not have them

ditto that.

So you wouldn't try pulling it and popping the clutch in 3rd? I hit the starter with 12v and that's how I determined the motor was stuck (will all the plugs out putting it in gear won't turn the motor over when you pull it, got 2 nice skid marks in the driveway where my kids forgot to tell me they'd put it in gear before we towed it to the barn).

I just don't want to cook the starter too.... so, a short sharp shock should see some significant success?

It is possible to bend rods doing that

Having time to think about it cleaning the barn today, I think I'll yank the hood/tank and look down the plug holes and see what's right there - chunky rust and I'll take the head off rather than bend/burn/break something for a quick fix.