The three holes adjust the stroke of the accelerator pump. The closest to the throttle shaft is summer, the furthest is winter and center by elimination spring & fall. Actually it does not matter much. I always find the center one with the most wear and on my rebuilds put the pin in the center hole. Only a fairly rapid acceleration needs the pump to reduce stumble. Therefore I suspect the problem you are experiencing is not with the pump but more likely the adjustment of the idle mixture screw. Most rebuilds I have done have the screw all the way in or only a fraction of a turn out.

@chip 

Hi Chip

Am I remembering right that the idle screw on an RJH-08.is an air screw rather than a fuel screw?

In other words, does turning the screw in actually give a richer mixture?

Thank you for your help on pin location.

In the booklet, Instruction and Care of Chevrolet Motor Cars for the International/AC has directions to adjust the carburetor on page 40.

Page 38, illustration 24 labels the screw as an idle adjustment screw.

Also, it shows an illustration that shows the connection for the fuel pump showing two holes, one for summer and one for winter.

I agree with Chip on the adjustment of the idle adjustment screw. Right now, I have the idle screw turned out to one full turn out. The car will idle not smoothly, and I think it is too much fuel for the carb to handle when pressing down on the gas pedal. Too much fuel stalls the car is my thinking about the idle adjustment??

The idle adjustment screw adjusts the dilution air that mixes with the mixture coming up the low speed jet (aka Idle tube). Wear to the carburetor body from rotation of the throttle shaft allows more air into the carburetor next to the throttle plate. Screwing in the screw helps to reduce that air and result in a better mixture at idle. Pushing the throttle pedal results in a temporary lean mixture that results in hesitation or "flat spot". If there is a popping sound the mixture is too lean. The instructions in the owner's or repair manual are for a carburetor that does not have a worn throttle shaft passage. Hence, the need to reduce dilution air. Yes, the carburetor body can be bushed to correct the wear but, it has proven to be an unnecessary expense if a good idle can be achieved with shutting off the dilution air. 

Hi Chip,

Are you still rebuilding these Carter RJH08's for customers?  

I have one that's in need of some help.  The low speed idle tube is likely to be completely blocked.

Thanks,  Jeff