I need some thoughts from those who know:

93 SE VE 240K was running fine- with the occasionally clattering VTCs. It has a CAI on it- I can hear the intake sound and know what it's supposed to sound like. First I noticed that the intake sound changed, and that power was down some. Then while I was under the hood I listened and it sounded a little like a scraping noise inside the valvecover on the rear bank around the VTC. At idle, I slowly disconnected the front coils and the engine ran on the back three.

A week or two later I noticed the intake sound changed again. Not long after, I smelled an oil leak and found that there was a crack forming in the valvecover around/over where the exhaust (I think... forget now) sprocket is. I pulled the front coil wires again at idle and the engine stalled. Parked car.

Regardless of the actual problem I haven't gone digging for the problem because I knew I was going to replace the VTCs and other stuff and it was more $ than I was ready to dig for. Now I'm ready to dig.

In my head, I'm speculating that the timing chain has worn/stretched more than the tensioner can deal with (or tensioner failed), and that the chain has jumped at least the exhaust sprocket if not both.

Am I right, or is there something else? If I'm right, how many teeth do you figure it could jump before smacking valves? Before anyone suggests- this engine is otherwise nearly pristine-clean internally, ran really well, and used maybe a half quart of oil in 6K miles on Mobil1- so I'm really inclined to keep that engine even if I have to tear stuff off of it.

Thanks

 

could the vtc end cap have broken like they always finally due and instead of falling
and busting out of the lower timing cover its jammed and busting out of your valve cover
where you say its cracked.?
can you pull the front valve cover and look?
its way easier than the rear, just re use the gasket
with oil resistant goop

 

exploratory surgery is the only absolute answer

 

It's the rear bank that's the problem.

You've given me a new possibility to think of. Actually, I'm trying to remember if I didn't hear some of that scraping noise before I noticed the intake sound change. Do you think the cap could have jumped the chain. Never-the-less, maybe it's a second problem.

 

Yeah, I know. Was just hoping for a few "seen that before" folks to throw in a few extra clues.

 

In addition to diagnosis, I guess I'm also asking how long the chains last on average. Nothing lasts forever... I figure the chains go too, eventually.

 

I know of no cases of a broken chain ever, failed tensioners and VTC caps yes, but the chain itself none.

 

Is the VTC cap just an issue of a piece floating around, or is there more to it?

Want to give any odds on bent valves?

 

bent valves are unlikely.
pieces floating around and the eventual complete failure with the accompanying destruction are the eventual fate

 

Accompanying Destruction??

 

I think that trnslates into "really bad". Probably the equivilant of a VG breaking a timing belt.