500e Exhaust Camshaft Broke!
 

Any suggestions:

Just replaced timing chain and guide rails (upper and lower), drove car roughly 600 miles and yesterday coming home from work (5-10mph traffic) engine stops dead. Turns out exhaust cam gear broke off shaft. Hopefully no other damage, valves appear ok and compression leak-down is well within spec.

Any ideas how or why this occurred. Is it possible to install chain too tight (and damage all cams?). Another symptom is that in the first 100 miles the car would occassionally not start on initial attempt, but would rev. up then die. Hitting gas right after ignition got it going, not consistent though.