Daniel and all,
I have a friend I used to work with at my old job who is the most amazing
mechanical engineer I have ever worked with. He worked for a number of years
at Ford Motor Company in their Advanced Engine Design Center. He is a major
gearhead way beyond what most of us understand in engine dynamics. I asked
him once about this very thing and (if my memory serves) he told me 1"
clearance around the circumference of the velocity stack and 3" clearance in
front of it is what the carb would consider "infinite space" as to not impede
airflow into the stack. He once talked about the turbulences created as air
goes in and what happens in the manifold, combustion chamber and exhaust
mani/header/pipe with airflow and turbulence. It was pretty intense the
level of detail.
He also mentioned that you don't want to create a pressurization of the box
as it will vary the intake pressure of the rear carbs. I think it was that
the air was forced into the box and had no where to go, creating more
pressure in the rear of the box and rear carb. The idea is to get cool air
to the carbs without creating differing pressure situations front/rear. He
said to put holes in the box at the rear (closest to the passenger firewall)
to relieve the offending pressure.
He did also mention that the intake tube had to be smooth inside so as to
not create turbulence and that the biggest filter you could afford and fit
onto the front end as to let in as much flow as possible.
Hope this helps...
A sidenote, once he told me of a turbocharged 2.0L experimental motor they
were working on that pushed 1000hp.....for about 10 minutes before the bottom
of the engine exploded. They used to get a kick out of building and testing
these insane motors and then "grenading" them from behind the dyno shield.
Talk about a fun job.
Stan Wada
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