Craig et al,
David Vizard did a fairly complete study on velocity stacks, as printed in
"Building BMC 'A'
Series Motors" and the upshot of his flow bench work was that the radius at the
end is the greatest determining factor in flow rates, not the length of the velo
stack. tThe length lends itself directly to the intake path length, which
affects the power at RPM only, NOT throughput (flow rate) . Per this treatise,
if your cam gives more horses at a higher RPM, you want a longer intake path,
and vice-versa.
Just my condensation. My .02?- go with a velo stack that fits without major
modification, and is as close as possible to your expected HP profile-You could
Dyno it of course.
Mark Haynes
Kerry Seibert wrote:
> GREG - try APT (Advanced Performance Technology) in Riverside, CA.
> www.aptfast.com They have all kinds of goodies that might help. I'm
> using their SU billet stub stacks on my 1 3/4" SUs and a K&N filter fits
> over the stack. Still fits under the bonnet of my Morgan.
>
> Craig Seibert 1968 Morgan +8 car no. 611 "Duff Morgan Racing"
>
> PS I've talked to a few people who say the "tall" velocity stacks (though
> they certainly look cool) are not as good as a good "stubby" stack as far as
> air flow and turbulence. APT seems to be one of them. I'm no expert nor
> engineer . .. . . . . just using what seems to work for me . . . . . .
>
> -----Original Message-----
> From: owner-vintage-race@autox.team.net
> [mailto:owner-vintage-race@autox.team.net]On Behalf Of
> Gregory_Schulz@mil-elect-tool.com
> Sent: Monday, May 22, 2000 4:13 PM
> To: vintage-race@autox.team.net
> Subject: Filters for velocity stacks
>
> A friend runs vel. stacks on twin SU's.
> He has round cylindrical "slip on" foam
> filters about 4 in. OD and approx. 6 in.
> in length. They are very low restriction
> but do manage to keep sand, stones, etc.
> out of the internals.
>
> It is of "one piece" construction, versus
> several pieces glued together. The filter
> shape is reinforced by large internal coil
> springs which capture the lip of the stack
> and holds the filter in position.
>
> They were on an ex-SCCA Sprite from Texas,
> I believe, and over time the source info
> has been lost.
>
> Does anyone know if something like this is
> still available somewhere?
>
> Thanks,
> Greg
> VSCDA #517 Sprite
> Cedarburg, WI
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