Tuning a Holley 4 bbl

[junkyardjeff]

I have a Holley 600 that has a slight bog just off idle so I presume its in the accelerator pump,what parts do I need to change to give it a longer squirt of fuel,I dont have a model number but its the one with the fixed floats.  I know it also needs to be richened up a little and would that cause the little bog and should I do that first.

[Learpilot]

I have a Holley 600 that has a slight bog just off idle so I presume its in the accelerator pump,what parts do I need to change to give it a longer squirt of fuel,I dont have a model number but its the one with the fixed floats.  I know it also needs to be richened up a little and would that cause the little bog and should I do that first.

First make sure the accelerator pump is not binding and is squrting a good stream. The next no cost way is to take out the flat head screw on the plastic cam on the accelerator pump and put it in the other hole. Next you can buy a different set of cams from Summit or Jegs or  a local speed shop. Next you can get a squirter that is larger, bigger number the bigger the size.
That is the way I fixed my Holley.
Rick

[wayne petty]

holley pump cam assortment  part number 20-12   available at many parts stores...

http://contentinfo.autozone.com/znetcs/product-info/en/US/hly/20-12/image/8/


you might also want to check that when you move the throttle off idle... that the pump lever that is mounted on the pump cover.. is moving instantly.. no wobble...    i had to shim with tiny washers the pump lever in my 4180... to get it to move instantly...  i plan on replacing the pump cover...

http://contentinfo.autozone.com/znetcs/product-info/en/US/hly/34-504/image/8/

[brucer]

i would try the discharge nozzle first..

[chimp koose]

You may want to try a little more initial advance in the spark timing.I always try to optimise ignition before getting into the carb much.changes to ignition timing will alter the vacuum signal to the carb .An off the line bog is not usually caused by a jetting issue since you would not yet be into the main metering circuit.Off the line performance is first dealt with by increasing spark advance until no improvement is found( this may require total advance to be reduced to avoid pinging). Then pump shooter size can be increased until bog is gone.A change of pump cam positon is usually done when launching a car from a higher rpm than off or near idle to provide good pump shot from the wider open throttle position.Please remember that whenever you change timing you should check idle speed and mixture.

[kb426]

Make sure the pump arm isn't bottoming out at full throttle.