accelerator pump adjustment
Burning Brakes
Joined: Jul 2005
Posts: 787
Likes: 0
It's important to realize until the idle mixture and ignition timing are correct the accelerator pump shouldnt be messed with, and if it still needs adjustment then only bring in the minimum extra pump to alleviate hesitation.
It's also important not to crutch the maladjusted/missing choke with improper idle mixture adjustments or crutch a poorly adjusted idle mixture with extra pump shot.
There are two kinds of adjustments......
The accelerator pump arm override is the bolt thru the spring right next to the front bowl.....basically, the metal arm on the underside of the bowl should still be able to move a bit even with the throttle wide open (obviously to be checked with the engine off).
The other is more fuel squirted or at a different rate. This involves three things;
- the screw holding the accel cam in place. there's a #1 and #2 marking each hole in the throttle arm. #2 makes the fuel squirt a tiny bit later.
- choice of accel cam (holley 600 VS has the orange cam which works well on most street engines). These are trial and error unless you really understand the physics of an engine.
- pump nozzle size. the larger the holes in the nozzle (marked on the side of the nozzle body), the quicker the pump shot is delivered.
If the timing and idle mixture are correct, the order of things to mess with is override adjustment, screw position, accel cam, nozzle size.
Its also worth noting if theyres anything wrong with the engine including vacuum leaks (hint; it won't idle worth a crap), you're just covering up problems.
It's also important not to crutch the maladjusted/missing choke with improper idle mixture adjustments or crutch a poorly adjusted idle mixture with extra pump shot.
There are two kinds of adjustments......
The accelerator pump arm override is the bolt thru the spring right next to the front bowl.....basically, the metal arm on the underside of the bowl should still be able to move a bit even with the throttle wide open (obviously to be checked with the engine off).
The other is more fuel squirted or at a different rate. This involves three things;
- the screw holding the accel cam in place. there's a #1 and #2 marking each hole in the throttle arm. #2 makes the fuel squirt a tiny bit later.
- choice of accel cam (holley 600 VS has the orange cam which works well on most street engines). These are trial and error unless you really understand the physics of an engine.
- pump nozzle size. the larger the holes in the nozzle (marked on the side of the nozzle body), the quicker the pump shot is delivered.
If the timing and idle mixture are correct, the order of things to mess with is override adjustment, screw position, accel cam, nozzle size.
Its also worth noting if theyres anything wrong with the engine including vacuum leaks (hint; it won't idle worth a crap), you're just covering up problems.
Last edited by evil herbavore; Nov 12, 2006 at 04:59 PM.
