Over twenty years ago I read a lengthy report written by an Engineering
class at a Midwestern University (US) on their Graduate Engineering project.
It was done on the flow characteristics of the (stock) Rootes aluminum head.
It I recall correctly, they determined the characteristics of a stock head,
and modified the chamber shape and ports to increase its efficiency without
hurting its "daily-driver on-street behavior" or hurting its longevity.
From what I remember, they concluded the intake ports needed to be
straightened as much as possible but must remain small and have a much
rougher (than stock) surface finish to encourage fuel to remain vaporized at
low speeds and low temperatures, and they said the intake "pathway" comes
into resonance (like a pipe organ) at around 14,500 rpm.
They also unshrouded the intake valve areas of the combustion chamber by
removing material which lowered the "static" compression ratio, however,
since the entire intake pathway was more efficient, it allowed more air-fuel
vapor to enter the combustion chamber and boosted its "dynamic" efficiency.
They were not allowed to cut away the valve guide stubs from within the
ports, as this study was directed at the improvement of mass-production
engines expected to have long service life, and the goal of the study was to
show there was a place for efficiency studies in the automotive industry.
I wish I had a copy of their report, or knew which school studied the
Rootes head. I know I read it prior to 1980.
Jim Leach PTC Seattle
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