Machining the outside port edge and inserting a sleeve works very well for
the early heads. Those heads (early ) were machined with a ball mill so
that there was not a chance of the manifold overlaping the port entrance.
Good theory, but dosen't get the job done for a racing engine. You might
think about calculating the gas speed therough the ports as a better method
of determining the shape. The speed through the valve is the fastest due to
the restriction of the valve and from this I have in the past recommended a
gradual taper to the valve so that the column of fuel loaded air is
increasing in speed up to the valve. Though this was not a mind boggler in
the flow bench it proved to be the best in the dyno. OR, you can just smooth
out the port some, do a careful valve grind and then go a half marker deeper
in braking and save all the hassle.
[This originally had way too much included text and exceeded the list message
size limit. I'm only a little bit nehind in admin stuff! mjb.]
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