A couple of months ago, my 74 450SLC apparently broke a chain rail and damaged the left cam gear pretty badly. I limped in to a local mechanic who replaced both cam gears, chain, tensioner and the broken rail. Amazingly, the car seems to run decently after this disaster. I assume this means I lucked out and avoided bent valves on that head (chain jumped only one tooth?).

I have since learned from this forum how common an occurance this is with these engines around 100K miles, and the usual preventive measure of replacing all the rails, tensioner, and checking chain stretch. This is what worries me -apparently only the one broken rail was replaced! Presumably this was the left inner (straight) rail- is this always the one that fails catastrphically? Or am I driving around with a time-bomb with another rail about to fail? Thinking about it, this might be the only rail positioned so that a broken piece would get between the chain and gear, or is it?

Hopefully somebody out there has seen enough of these to enlighten me, thanks!