At the advice of a fellow over on Thumbertalk, I tested my new pumper on my bench by filling the fuel bowl and actuating the throttle mechanism and testing the accelerator pump. The idea of the pump is that when you open the throttle, that creates an extreme lean condition for a short time until the normal fuel delivery can catch up. So the pumper injects a jet of fuel into the air stream when the throttle is actuated to compensate - thus the instant throttle response and no lean condition off the start.

Here's a short video clip of the test - you can't see the stream real well but if you look closely you can - the stream comes from the little brass nub poking up in the intake side. You can hear it pretty well, though:

VIDEO (Quicktime, 3 Meg)

Bill_P over at thumpertalk has his running very well and based on my results recommends doing the taffy mod that GreenKLX referred to. He says at wide-open throttle the pumper stream works best when it last for about 1 second. Mine lasts for almost three seconds, but the stream duration is proportional to how much you open the throttle and it's a lot shorter at shorter throttle turns. Bill says if the stream is on for too long, it makes an overly rich condition and causes it to bog on startup.

I think I'm going to leave it as is for now and test how it runs. But I'll get the parts and be read to do the taffy mod if I detect any bog off the start.



Edit: link to video no longer works

 

Pretty cool, cant wait until it's all put back together.

 

Anything like this?

 

Cute, Mav [sm=chairshot.gif]

 

thats pretty cool there nobrakes, so a pumper carp "pumps" the gas into the motor... not too framiliar with them...

 

Find a car with a carburator on it. Take off the air cleaner and have someone step on the gas pedal. You will see at least two streams of raw fuel being shot into the venturi to mix with the air coming in.

The heavier the vehicle, the more raw fuel shot you need. I was running a 3500 pound car with an automatic tranny. I built up a Holley 3310 with dual accelerator pumps of 70 cc's per side. That was a total of 140 cc's of raw fuel being shot into the carb to make that 440 cubic inch engine jump to life!

This is what it looked like!


That's a squirter in action!