Some of the detractors of belt driven cams complain about "interference" engines that suffer damage when a belt breaks. Not all are. Seems like many of the popular V8s needed piston machining just to create safe running clearance if a very frisky cam is installed. Or, start missing on a few cylinders if my punk cousin downshifted his hot mom's stock V8 Mustang into second at full speed. So, if the chain broke or even wore and jumped a link or 3 the wrong way I'm guessing the pistons could whack the valves in more engines than suspected. Surely Ford 302s and inline 6s were among the ones that had plastic sprockets that would fail badly at mileages approaching 100K.