If a Timing chain snaps on an 85 300D engine, will the valves hit the pistons and destroy the engine? Or would there be no damage, just a temporarily diabled engine.
What woul happen to a 85 300D engine if a Timing Chain snapped on the road at 40 mph, 4 passenger load.

worse case - broke/bent valves and holes/damage to tops of pistons.

Not Good...
 

The valves will hit the pistons :(, no question about it. I've only seen one chain failure on a 617. It broke the camshaft. The bottom end was okay though :).
Regards,
Randy D.