<VV> Carter AFB on 66 140

[Tony Underwood]

At 01:30 PM 6/8/2007, Matt Nall wrote:
>If your carb is standard practice jetting NOW.....  just reverse the 
>primary / secondary jets....  done it many times with no ill effects!
>
>Secondaries have no metering rod and are smaller dia.
>
>Also,  if available...a softer spring on the MR's will let it drop 
>at a lower vacuum!


THIS is the way to control fuel metering in an AFB, via those 
springs.   Sometimes in sterner situations you MIGHT have to change 
the primary jets but almost always it's metering rods and 
springs.   Never ever had to change a jet on any AFB.     I'd not 
recommend it myself.

It's ALL about metering rods.

By the way, a puff of black smoke when starting out while running an 
AFB is almost always the sign for a softer spring set for the 
metering rods.   A 'Vair engine is small displacement and there's so 
little volume in the intake system...  crack the throttle more than a 
little bit and intake vacuum drops to almost nothing RIGHT NOW and 
those springs slam up, metering rods jerk out of the jets which then 
dump lots of fuel into the carb's metering system, and there goes the 
puff of sooty smoke out the tailpipes, and your mileage along with it.

Softer springs...  in fact, *very* soft...  keep those metering rods 
under control and have them open up ONLY under very low vacuum 
conditions.    That all by itself will make a big difference in an 
AFB's fuel mileage capabilities, especially with around-town 
driving.    And the metering rods and springs are SO easy to change 
on an AFB... all you need is a screwdriver and a minute.


Haunt Ebay and pick up a Carter "Strip Kit" metering rod kit, best 
thing for tuning an AFB for best effect.    You'll likely not get 
springs with the kit, depending on which one you find...  might have 
to check around the hotrod shops for softer springs, or "roll your 
own" from just about any spring stock you might be able to turn up 
from whatever or where ever.     It's the traditional hotrodder way...

Or, you can use the rods in the Strip Kit which lean the mixture 
through the maximum travel (no steps through most of their length 
until the end), which accomplishes pretty much the same 
thing.   Experiment with them.



>Always remember.....   no 2 FACTORY built cars/ engine  run the same...


Hell, no two engines act alike even when carefully custom built to be 
identical.     Your logic here is on the money...

Hotrodder's rule of thumb:

Forget the rule books, run what the engine likes to run.



tony..      gots AFBs