<VV> ball and spring and pump cup

[Grant Young]

As to the question on the mystery secondary carb. It is most likely an early 1960 carb that some folks mistake as a secondary since it looks different and does not have a choke. Not sure when GM changed from the ball and spring (which was used in many carbs of the era) to the needle, but I don't see many of them. These are also sometimes used in the secondary position with the old Otto rotator set ups. There is another problem when that is done, however, as they do not have the chip in the throttle plate and are therefore more difficult to adjust unless the plate is changed to a later one (so it is better to use a 62/3 base and 1960 bowl cover). The ball and spring can be reused or a brass needle can be added in their place on a rebuild. The top of the hole is cut larger and with a slot, but it doesn't seem to have any effect on the fuel squirt volume.

As for pump cups on the secondary carbs...they should be used if the carb has a passage between the accelerator pump housing and the hole for the brass needle. This can be determined by the presence of a rivet on the outside of the accelerator pump cavity. Smog secondaries do not have this passage (or rivet)and should therefore not use a pump cup. They do, however, still need the return spring as it is necessary for proper throttle operation. 

The Carbmeister