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 accelerator pump 3rd hole ? 
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Joined: Tue May 06, 2014 5:34 pm
Posts: 45
The other day I was looking at a NHRA stock eliminator race car equipped with a Qjet and noticed the carb builder had drilled a third hole in the acc pump lever, inboard of the two usual ones.

I checked on one of my Qjet and it made me realize that when we use the inner hole (like we almost always do), with the carb at full throttle, there is still some pump stroke left, not used, so to speak.

I then modified a lever I had with a third hole that I drilled, and assembled it on a Qjet I had at home. I don't have the numbers off the top of my head, but it did increase the stroke to almost the very bottom.

Won't be able to try this on the road before spring, but was wondering if any of you guys ever tried or thought about this.

Wed Nov 30, 2016 10:28 pm

Joined: Tue May 23, 2017 9:40 am
Posts: 1
Some Quadrajet builders of NHRA Stock and Super Stock Quadrajets do drill a third hole for accelerator pump travel but that's just part of getting the 21/32 maximum pump travel. Using a pump that has a short duration spring and a long stem so it can be trimmed allows you to set the pump cup just a tad above the fill slot. Pump shot is important in a car that foot-brakes but a lot of class cars use a 2-step to launch where by the accelerator pedal is "matted." In those applications the accelerator pump is just needed mainly for initial cold starts. I used to set up all carbs with full pump travel even though the customer may be using a 2-step but somewhere down the line he may want to try foot-braking or that carb may be sold to a foot-brake racer and it will already be set-up for that application. If you do plan to do some serious pump work, do yourself a favor and get a pump rod that uses a hair pin cotter so you can remove the airhorn without having to drive out the roll pin in the pump lever. They are still available new from quadrajet parts suppliers. Hope this helps.

Tue May 23, 2017 3:11 pm
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