Thanks for the empathy and advice. Definitely don't need any of the metal bits and glitter fouling things up. Everything but the lines that run along the passenger side will be cleaned in the machinist's equipment. He uses a jet washer, then an ultrasonic tank, then a media blast. I'll either clean the lines and hoses myself or replace them, depending on how they look. I'm not looking forward to the oily mess!

Don't forget the oil coolers.
Bob B

The hard lines from the t-stat to the cooler are not hard to clean. When you remove the t-stat and the cooler, which is of course the hardest part and use patience to avoid trashing the t-stat and cooler male threads, you have clear access to both ends.

I tie a few heavy washers to a long & strong piece of cord. On the other end I wrap the cord around a piece of rag. I hose the rag with brake parts cleaner and also squirt a lot into the line itself and shake it around. Pull the cord through the line and it'll swab out the oil residue and crud. I do this several times and use a new piece of rag as needed until the rag comes out clean.

You definitely need to open the t-stat because there's some hiding spots in there where crud can collect. It's in the bypass/overpressure section of the t-stat (the smaller of the two screw-on cap locations) where the crud collects

http://forums.pelicanparts.com/uploa...1355162717.jpg

Oil coolers for sure!http://forums.pelicanparts.com/suppo...eys/gitaar.gif

Great tips, KTL, thank you. I've been reading up on oil line cleaning, and people seem to have success with the method you describe. I'll give it a shot.

Oh my Goodness.

Break a Leg Brother, wow I feel very bad for you.

+1 split and clean.

Pop analysis - as the three (did you say) bolts started backing out, they started forcing the chain out toward the tips of the teeth on that IS gear. This kept putting more and more force on those tips, and they started breaking. Along the line perhaps ends of rivets on the chain started wearing also. Finally either one chain link connector piece fell off and things got worse in a hurry, or one bolt finally got wedged between chain and the stubs left of the gear. Either that broke the chain, or the combined resistance of six valves hitting the heads broke the camel's back.

I don't think the chain could have been installed with the chain offset to the engine side. It would have made a heck of a racket right off the bat.

But once a bolt or bolts started backing out, things could have gone bad in a hurry. The chain rubbing on the bolt heads would be in the direction of loosening those bolts, wouldn't it? Not a lot of relative motion, but you wouldn't need a lot.

Could be a good theory. For what it's worth, here is a pic of the IMS gear where the three bolts came loose. Pay no mind to cracks in the gear. I pressed it off the shaft with no regard to its integrity, reputation or future.
http://forums.pelicanparts.com/uploa...1530167603.JPG

The remnants of the broken chain were jammed between one of the gears and the case. Took some effort over an hour or so to dislodge it. The bolts that backed out were all passed through to the cam chain housing rounded off and beat up. That is, none were jammed in the gears.

Still puzzled as to how this could happen more than 26k miles over several years since the motor was last assembled. I would think if it were to happen it would have happened at 100 miles or 300,000 miles....

On further refection, it was the chain breaking which was the immediate cause of the broken rockers (on only that one side). So valves hitting pistons weren't a cause of the chain breaking.

Still a rather unusual mishap. None of the guys who read these posts and have disassembled hundreds of engines and more have said they have seen anything similar.

From the pictures, it looks like the teeth on the outer (rear) row on the steel IS gear are largely undamaged, while the inner ones are very much damaged. In addition, the first picture shows the idler gear on the tensioner arm to have way more wear - on its outside - than is normal. This makes me wonder if all along the chain was not properly placed on the IS gear, and was riding only on the inner row? That would place it very close to those bolt heads. Doesn't explain the apparent lack of noise - you'd expect that much of a mismatch in chain alignment to create a heck of a racket - but otherwise sort of fits what we see. When rebuilding an engine, or even just adding pressure fed tensioners, it is easy enough to have the chain fall off the IS teeth (especially if the engine is on a stand and that side is up). Just randomly pulling the chain back out won't necessarily get it onto the two rows of teeth.

Walt, thanks for your thoughts. Part of the scenario you describe makes sense to me; part doesn't. I'm not much into metals, but the damage on the inside teeth of the inner row of the IS gear looks like it might have happened either suddenly or over a very short period of time. The sharp edges lead me to this possible conclusion. I would think that if the chain had been rattling around for a while that there would be more rounding on the edges.

Is it possible that this damage could have occurred over 26k miles?
Is it possible that the chain could have jumped to the inner row more recently and if so what might cause that?

I wouldn't be as surprised to learn that I assembled the chain incorrectly as I would to learn that it lasted 26k miles like that.

Thanks again :)

Wow, does time ever fly. Finally boxed everything and drove it to the machinist for inspection and a thorough cleaning. He still needs to disassemble the heads and have a close look at the valves etc.., but it looks like I got off easy. No damage to anything but the rocker arms, intermediate shaft gear, cam gear and timing chain. I'll replace the idler arm sprockets and maybe a couple other things. The other good news is that the crank shaft and all the bearings looked to be in excellent shape---no fouling from metal debris and the bearings in good enough condition that they don't need to be replaced. My retirement savings are relieved!