looks neat, trying to understand it, its been MANY years since I toyed with this stuff. can you explain a little more for me.......if you get a second........I think I have all the different cams and different pump sizes and nozzles here from the 70's and spent many a wee hour playing with my holley setup without totally understanding what I was doing....kinda like the way I do now.....
 
thanks
 
RR

Crisp throttle response comes from a well tuned Accelerator Pump.
(3) things with Accelerator Pumps:
(1) How Much (2) How Fast (3) How Long.
 
PUMP CAM profile lift and slope determine
VOLUME and TIMING of FUEL delivery to the NOZZLE.  
 
PUMP NOZZLE SIZE determines the RATE OF DELIVERY
or HOW LONG to deliver the VOLUME determined by the CAM.
 
Holley 1850 Throttle Plate used to get data.
Primary Idle Speed Screw was completely closed,
then bumped opened about 1/8 turn before setting indicator zero.
 
Idle speed setting determines Butterfly Shaft Park Position.
PUMP CAMS are mounted on the throttle shaft end plates.
Shaft Park Position determines Pump Cam Starting Point,
which can increase or decrease cam profile total lift.
 
Hole #1 activates the pump a little early,
relative to throttle shaft park position,
and delivers a good pump shot right off idle.
as butterflies start out from a fairly closed park position.
Generally, for 600 to 900 RPM idle speeds.
 
Hole #2 activates the pump a little later,
delays pump action relative to throttle shaft position,  
as butterflies start out further opened from a closed position.
Generally, for around 1000 RPM idle or above.
 
When #40 or larger accelerator pump nozzle is installed,
Holley #26-12 Hollow Pump Nozzle Screw should be used.
 
When #37 or larger accelerator pump nozzle is installed,
Holley #20-11 50cc Pump Conversion Kit should be used.

go on youtube and search holley tuning and check out some of the video's to get ''back into tune'' so to speak  
 
Norm