<VV> Power Enrichment /Accelerator pump circuits

[Sethracer@aol.com]

In a message dated 10/8/2004 7:03:07 AM Pacific Standard Time,  
dmonasterio@megared.net.mx writes:

Bob,
I think that the brass needle moves upward when  the accelerator pump moves
down, sending fuel to the passage below the  brass needle, allowing fuel to be
skirted thru the 2 tiny holes. Please,  correct me if wrong.

Daniel

<<What makes the  pump discharge needle work, when all it is, is a piece of
> brass with a  point, sitting  in a hole?
>
> Engine vacuum pulls the brass  needle off its seat. That allows a flow of 
gas
> from the internal  restriction (jet).>>




I feel like the person in the old Certs commercial - Stop - You're both  
right!
 
The problem is that the original questioner (Russ) mixed up two  circuits - 
since his letter had three questions, that's not too bad.  First  he asked 
about the high speed enrichment needle and whether it belonged in a  secondary 
carb. Bob rightly answered no. But there was (at least originally) no  place for 
it in a secondary anyway. There is no high speed circuit  installed in a 
secondary carb. My guess is that someone swapped on some  extra primary carbs. Then 
he asked about accelerator pumps cups. Bob answered  the normal reply that 
cups should be removed in secondaries, since they are not  normally needed. 
Finally, Russ asked about the pump discharge needles and how  they worked. Here 
Bob answered the correct answer for the high speed enrichment  circuit needles. 
Oops. As Daniel said, the needles in the accelerator discharge  circuit are 
lifted off by accelerator pump discharge pressure. Those needles are  put there 
to keep engine vacuum from the venturi from sucking out the fuel  stored for 
pump use. 
An old racing tip was to remove those needles and grind a slot or two on  the 
sides of them (across where they seat) usually with a file, then re-install.  
This lets the accelerator circuit bleed a little bit of extra fuel in at high 
 air volume through the carbs, sort of an auxiliary high speed enrichment  
circuit. One other note, if you want to disable a factory high speed enrichment  
circuit in a primary carb - say for use as a secondary - you can just use the 
 wrong gasket that comes in the kit. Most kits have two different ones to go  
under the cluster. If you use the one without the hole over the brass 
plunger,  you have eliminated the high speed enrichment circuit! - Seth  Emerson