My 1978 450SL died a few weeks ago. My mechanic said it was "probably" the timing chain. I'm bothered by the "prpobably" bit. ... as the engine freely cranks, shouldn't a simple compression test tell whether the chain jumped and bent the intake valves? Also, I didn't hear a loud "Bang" when it died. Instead, there was the sound much like a waste gate releasing ... a loud "air release" sound. For what it's worth, the trans was slipping the past 4 weeks. Your advice? could it be something other than the dreaded timing chain problem? is there an easy way to verify prior to ordering a new engine? Thanks much!

Remove 4 bolts (10mm) either side and the valve covers are off. This will give you a visual check of the timing chains.