[TJ's GMC]

Originally Posted by Ancientx

Wow! This is EXACTLY the same thing that happened to "Happy Truck". Changed plugs before leaving WY, got to Canton SD, parked for the day at a car show, hopped in and it started happening.
A local mechanic told me it'd spun a main bearing and it's sat for 4 years.

I have hope!! WOOHOO!

I watched your youtube vid and it sounds EXACTLY the same.

Maybe I won't have to rebuild/replace it!

Not to spoil your bubble...but I wouldn't count on it being some crap that fell in the piston....You say you changed the plugs before you left...then when you arrived to SD you let it sit for a few hours...fire it up and it starts knocking? Its possible a piece of carbon...but do be careful. It could have spun a bearing. Mine started knocking RIGHT after I changed the plugs which indicated some crap falling into the cylinder. But if yours happened several miles later it could be worse. Sorry to sound grim...just don't get your hopes up to high. lol