[Johan]

Well, Watkins Glen Blows motors because 10000 rpm is what you get if you go from 4th to 2nd too soon. The valves hit the pistons. Other mechanical failures occur because the engine is new and has dyno time only. Bigger teams run engines around and test them before race day. For other teams, race day IS test day. Ford Gt's all had failed trans input shafts during the 1967 Daytona 24hrs due to poor metalurgy in the shaft billetts. All new, all failed, except I think one gt40 with an old shaft. Overheating is a big problem too and changes mechanical relationships and interfaces. Also, Johnny hotshoe can ruin anything given a chance. Most successful race drivers are easier on the equipment than a novice, especially transmissions.
This is why I drive the junker, er I mean, the tried and tested car I drive, for dependability !