First I ever heard of this type of nonsense happening. Then the traditional carnage ensued.

And the fallout.

Broke the top off.

 

That sucks. Valves hurt?

What brand?

 

Valves seemed fine but since I was elbow deep into the ol' girl ( basically had her stripped to the block, from the pan to the head) I swapped the head out with a freshly rebuilt one I had lying around.
Couldn't tell you the brand....had the whole long block rebuilt less than 20,000 ago by a company that used to be reputable but has since gone to crap. Out of blind respect, I won't mention the "companies" name.
Haven't heard of this sorta thing happening with the metal guides, though. Just thought it was interesting so I threw it out there.

 

Is there a brand name stamped on the chain tensioner? OSK stuff is usually stamped/etched on the tensioners and I think the sprockets also.

 

Was the chain found intact, or parted??

Looks to me as if an already broken chain might have grabbed and broken that guide and then carried the broken piece to the crank sprocket area.

 

Happened on start up. Turned, started for a second, then just shut off. Not nearly the noise you'd expect. Chain was sheared in two. Just kinda assumed the metal broke off, got dragged down to the sprocket, and stretched/broke the chain when it got eaten. Like I said, chain only had 20 k on it so I didn't really think that it was the culprit. Who knows. Was also thinking that the guide could have been whacked around when the mechanic installed the head.

 

Oh, and this happened months ago and I didn't save any of the parts. Don't recall seeing a manufacturers stamp on the guides or the sproket.