Rated speed of the crankshaft and the service life of the engine

Exceeding the rated speed of the crankshaft will shorten the life of your engine. If you run the engine too fast, uncontrolled vibrations in the crankshaft or valve train can occur. If the vibrations are too high, mechanical damage to the crank mechanism or valve mechanism may follow. In the worst case, a piston seizure occurs, the piston cracks or the crankshaft breaks. As a rule, this means expensive repairs or even complete failure of the engine. Ford recommends 5540 min^-1 as a continuous rpm for Endura engines (5350 min^-1 for Endura-DE) and 5950 min^-1 for both Zetec engines.