RE: Over-reving

[Max Dufford <max@xxxxxxxxxx>]

Sean,
 The issue of M3 over rev damage is one of piston to valve contact. For
many engines produced it is virtually impossible, barring valve keeper
or retainer failure, for the valves to contact the pistons. These
engines can go so far as to have the timing belt/chain break and suffer
no damage to the valve train. 
 
 Why can other engines take these abuses and the M3 can't? Well to make
it real simple, it a matter of piston clearance, camshaft timing/lift,
and valve spring rates. The more fire breathing an engine with high
compression pistons, high lift/high duration camshafts the closer to the
edge you are to the perils of piston to valve contact. In what I
understand of the M3's problem, valve float, the valves are just staying
slightly open at high rpm's when they shouldn't, hit 9,10 or 12 grand,
bam you have bent a whole bunch'a valves.

 This class action stuff would be a real issue if M3's experienced valve
float routinely at 6500 rpm's, but it doesn't. There are fixes available
if you want to wind that baby up, but that will cost you $$. If you make
a mistake with you expensive toy, learn from it, don't go looking for a
scapegoat.

Max Dufford
97 M3

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