If the opening in the phenolic block were smaller than the matching
opening in the manifold, presenting an obstructive step in the flow
path, that would be more intrusive, I would think, than the situation as
described; i.e., the opening in the manifold is smaller than the opening
in the phenolic block, presenting a lip, or "dropoff". Fluid flow past a
sharp-edged dropoff will produce localized turbulence, or backflow, but
the degree of the effect is determined by a number of variables: speed
of flow, density of the fluid, shape and size of the lip.
I agree with Ronnie that it would be fun to compare the flow effects of
these different situations, but then my motto is: "More Data Is Better
Than Less".
Gary McCormick
'70 2000
San Jose, CA
********************************************
Ronnie Day wrote:
>
> Gary said:
>
> >Matching the bores when there is such a small step size, and especially
> >if they are smaller, rather than larger, than the phenolic blocks, is,
> >as some other posts mention, probably not worth the effort.
>
> I'm not so sure. Even a small and/or partial lip anywhere in the airflow
> path MIGHT tend to create interference swirls far out of proportion with
> what you'd think. You're pushing the air column against and past a (so to
> speak) flat wall. Has anyone seen any photos of airflow under these
> conditions? Of course you could just measure the difference, if any, in
> airflow between unmatched and matched ports, but that would be as much
> fun to look at.<G>
>
> It would also be interesting to find out at what point a difference in
> manifold and port size does become a major factor. For instance, the SU
> (SSS) intake for an L-16 has 1 1/2 inch ports whereas the OEM L-16 heads
> had 1 1/4 ports. It would be interesting to compare flow with that
> combination, with the head opened up to match (Street Prepared legal) and
> with the SSS 1 1/2 inch port head. That info may be floating around
> somewhere or you might be able to model it in one of the desktop engine
> programs.
>
> FWIW, Ron
>
> Ronnie Day
> rday@cyberramp.net
> ___________
> The ACL Group
> Arlington, Texas
> (817) 572-0873 (V)
> (817) 478-2896 (F)
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