Accelerator Pump Diaphragm - 440 Six Pack

[MoparHonda]

What is the correct accelerator pump diaphragm to use on a 440 six pack?

My '70 Plymouth GTX with the 440 six pack runs well, but i get a slight hesitation when hitting the gas pedal while running at speed. If I'm in 4th gear (or any gear) running along at any speed and I hit the gas I get a slight hesitation before the car takes off.

(Stock engine, mild purple cam, electronic ignition.)

 

[62MAX]

What is the correct accelerator pump diaphragm to use on a 440 six pack?

My '70 Plymouth GTX with the 440 six pack runs well, but i get a slight hesitation when hitting the gas pedal while running at speed. If I'm in 4th gear (or any gear) running along at any speed and I hit the gas I get a slight hesitation before the car takes off.
(Stock engine, mild purple cam, electronic ignition.)

If you feel it's with the pump,the diaphragm is not the problem,you need to adjust the pump lever.The correct way is to remove the carb,back the speed adjusting screw out so the throttle blades are completely closed,then open throttle completely,lift the accelerator pump lever as far as it will go,measure distance between pump lever and screw,you should have .050/.060 clearance.

 

[BSB67]

Most light throttle hesitation that I've experienced was never the diaphragm, always idle or tradition circuit, usually fixed with a rebuild. Make sure your outer carb idle is not too lean.

 

[66Satellite47]

The "accelerator pump" does not have a diaphragm. It is on the center carb and has a cam & a squirter (shooter). I think you may mean the outboard carb diaphragm springs. I would start by removing the lead plugs covering the end carb idle mixture screws(front of each baseplate) & richen them approx. 1/4 turn. On the underside of the end carb baseplates is the idle set screw, opening that may also help. Then try different springs in the diaphragms. There is a package of different accelerator pump cams available, try some and different shooter sizes. All of my mine wanted 1 step larger than the stock size. Trial & error is required.

 

[BSB67]

The fuel from the accelerator shot, or squirter is delivered by the pump diaphragm on Holley carbs.

To the OP. Again, it is unlikely that anything in the squirter delivery system needs to be changed, unless something identifiable is wrong with it.

 

[66Satellite47]

The fuel from the accelerator shot, or squirter is delivered by the pump diaphragm on Holley carbs.

To the OP. Again, it is unlikely that anything in the squirter delivery system needs to be changed, unless something identifiable is wrong with it.

Ok, the lever/cam activates a diaphragm. To my knowledge there are 2 available, one the standard 30 cc the other a 50 cc. each have a different diaphragm housing. Shooter size is a very common tuning tool. Secondary vacuum spring tuning MAY be needed.

 

[MoparHonda]

Thank you for all your help, looks like I'm going to be doing some trial and error work.

 

[66Satellite47]

That's what it took for me, after understanding how the 6 BBL worked & what other folks that made them run good had done. Lots of real BAD info back in the early/mid '70's. End carb idle mixture screws & end carb idle screw(under the baseplate) 1st place to start. Slight center carb jet & squirter changes. Those get you in the ball park. BTW I ran the aluminum manifold w/ heat passage blocked off.