Re:TS = more power?

[christian147@domain.elided]

>I'm sure that the bigger valves were the driving force behind the twin 
>spark head.   All the dyno charts I've seen bigger valves have very 
>significant impact on high-rpm power production.  The better combustion 
>characteristics of the twin spark were gravy compared to the better 
>breathing of the bigger valves.   They probably wouldn't have bothered 
>to add all that complexity if they already had the big valves.

Mark I'm not so sure about that on the 90 degree heads.  Big valves don't
necessarily make a good head.  You need to maintain velocity as much as
possible.  The relationships are such that if you can increase velocity
by 4% and loose only 4% in bulk flow you will gain 4% in cylinder
filling.  If you loose 4% in velocity to gain 4% in bulk flow you will
loose 4% in cylinder filling.  I am not convinced this was well
understood by ALFA at the time, at least not in objective terms.  ALFA's
round ports offer no stabilization to the air column and so risk port
turbulence at higher velocity.  The ports and valves tend to be large for
the speeds they seem to intend to be run at, as if trying to keep
velocity down.  

Chris Hall
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