The organ pipe analogy is a pretty good one, as we tuned for better charge for a
given RPM range......We needed more power quickly on shorter tracks ( 1/4 to 1/2
mile ) than on larger tracks ( 1/2 to 1 mile ). Shorter stacks on smaller
tracks....Longer stacks on larger tracks....We wanted a flatter curve on the
larger
tracks, the trick was to run out of rpms near the end of the straights in both
cases , this was accomplished by taller Halibrand Q/C gears, engine hardware
tuning
& fiddling with the injection ( pills, metering blocks, nozzles, stacks &
pressure
)....Remember, the Offy had HUGE 4 valve ports and only 4 cylinders......for
large
& small engines.....
Brian Evans wrote:
> Did your results differ significantly from Vizards published work? BTW, I
> always thought that the different height stacks on the SBC injection were
> to tune the ports slightly differently to get a wider powerband - am I out
> to lunch?
>
> Brian
>
> Brian
>
> At 01:45 PM 05/25/2000 -0400, Arthur Blackwell wrote:
> >Gee, I guess all that work we did on stacks for the Hilborn Fuel Injection
> >for the
> >Offy & SBC doesn't mean anything.......;-).....
> >
> >Mark Haynes wrote:
> >
> > > 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
> >
> >--
> >Art Blackwell
> >Denver, CO
> >
> >" Even in the future nothing works " Dark Helmet " Spaceballs "
--
Art Blackwell
Denver, CO
" Even in the future nothing works " Dark Helmet " Spaceballs "
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