Re: old design was oilheads-digest V1 #47

[Tpcutter@xxxxxxx]

In a message dated 1/6/04 7:40:07 AM Eastern Standard Time, egrohe@xxxxxxxxxx 
writes:
<<The BMW design offers the chance for playing with the  rocker ratio of the
rocker arm.  This allows faster valve opening than a direct acting cam while
not having too steep ramps on the cam. It increases longevity, a BMW trait.
How many 200,000 mile R1's are there out there?>>

    I had sworn to stay out of this thread, but the above statement makes an 
assumption that is repeatedly proven wrong by performance tuners using rocker 
arms: rocker arms induce severe side-loading on valve components, causing 
accellerated valve, guide and seat wear. As it is much harder to properly cool and 
lubricate those parts than a camshaft, the advantage is more than offset.

    BMW has discovered, as have I and most other BMW race-tuners, that the 
maximum practical rocker ratio is 1.39:1. More than that causes geometry and 
reliability problems.

Tom Cutter

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