when did the autolite 4100 accelerator pump style change?

[cleandan]

I am working on an Autolite 4100 carb and am wondering when they changed the accelerator pump styles?
One style has the basically open chamber with the small one way flow diaphragm.
The other style has a casting in the cavity that channels fuel into the chamber while using a check ball and a limiter screw. (what I'm working on now)

I have rebuilt these before (both styles) but have never researched when these things changed.
I started looking around the net and can find reference to the check ball style accelerator pump cavity, but only in the 2100, so I figured I would ask here because you guys know all the stuff.

This is turning into a frankencarb, but still, I would like to know the basic date of the main body of this 4100.

Thanks and have a great day.
 

[cleandan]

I am surprised nobody has an idea when the Autolite changed the casting in the accelerator pump area.

C'mon guys, you are sort of like Mikey...except where Mikey hates everything, you guys know everything.

[rockhouse66]

If we are talking about what I call a "short nose" or "long nose" Autolite, my Sept. 1965 small block car has a short nose so the change was certainly earlier.

[cleandan]

If we are talking about what I call a "short nose" or "long nose" Autolite, my Sept. 1965 small block car has a short nose so the change was certainly earlier.

I don't know the technical name for this change, but sure, "short and long nose" would work.

The long nose housing is deeper, it has a cast in the body set of post you can see protruding into the accelerator pump cavity and there is a check ball in the post that is held in place via an external screw that come in the top of the cavity and is screwed from the outside into the cavity to keep the check ball from coming out.

The short nose housing is shallower, is basically empty, and it contains the umbrella one way check valve as seen in many various pump housings from yard sprayers, to carbs, to...well, a jillion other pumps using this version of a valve.

I'm just trying to get a timeframe when this casting change happened for no other reason than I would like to know.

Thanks for your input as it does help some.

My best guess is this change happened some time in 1964.