I drove with my F engine at 80 mph a couple times after seeing an old ad claiming it was capable of cruising at that speed. On one of those drives the various parts of the engine realized they had irreconcilable differences and broke up at 80 mph on the freeway. Now I have a 2F under the my hood; which has a slight dent that points upward where I believe it was hit with a lifter that I never found.