[AT] OT: Carbruators

[pga2 at hot1.net]

Exactly, Lou. I used to have a formula that gave the maximum
carb size in CFM of air flow for any engine. It took into
account displacement and maximum RPM intended in the primary
use of the engine. At 6,000 RPM a Chevy 350 needs no more
than a 650 CFM carb. More carb won't make it perform any better.

Phil

----- Original Message -----
>From    : Louis <louis at kellnet.com>
Sent    : Thu, 30 Dec 2004 22:39:42 -0500
To      : 'Antique tractor email discussion group' <at at lists.antique-
tractor.com>
Subject : RE: [AT] OT: Carbruators

>AFB is a design by Carter.  You can still buy that basic carburetor
design today.  Eldebrock and Carter are making them.  I have used a lot
of different carburetors on hopped up Chevy 350's.  I think that the AFB
is the best design.  They are simple and work great, compared to the
Holley's.  Holley is a brand. Quadrajet is GM's 4 barrel carburetor.
Quadrajet's are a spread bore carburetors, meaning the secondaries are
larger then the primaries.  I believe the AFB's are all square bore
carbs, meaning the secondaries and primaries are the same size.  Carter
and Holley produce square bore and spread bore carburetors.  Then you
have mechanical or vacuum secondaries.

  You need to consider the size also (here I am speaking mostly of
square bore carbs).  A smaller CFM will produce more low end torque, but
you loose on the top end.  But, you need an engine the has top end.  The
larger the CFM the less low end torque, but more top end you will have.
I have always run in the 600 - 650 CFM range on Chevy 350's producing
between 340 to 460 hp.  I know guys that have put 750 CFM Holley's on
top of their Chevy's, thinking that is what they need.  I would talk
them into trying my 600 CFM Carter.  They were amazed at how much better
their engines performed.  Most of these hopped engines were in either
Jeep's or 4X4 trucks.  So the motors aren't built to run a NASCAR race,
they are built to pull and go off road, so you want low end torque.  On
these engines you won't run out of carburetor with a 600 CFM carburetor,
they all run below 5,500 RPM. A spread bore well tend to produce low end
torque, because of the smaller primary. I rambled on long enough.

Lou