Weber - weird air correction screw

[EdHut]

Hi All,

I'm busy with project 28 'Carburetor rebuild' (great book Wayne!) and have taken one carb apart. I noticed that one of the air correction screws has different shape. It's the middle one in the photo.

I'm wondering if I should replace it with a 'normal' shaped one. This one didn't cause any problems while adjusting my carbs (some others did, so that's why I'm rebuilding it).

Quick other question: one carb has type "40IDA3C1" (and serial number 1688) stamped on it, while the other one is missing the "1", so it's a "40IDA3C", with serial sumber 1611). What are the differences, if any?

All advice greatly appreciated.

[cds72911]

40IDA3C and 40IDA3C1 are just left and right part numbers. Not a problem.


Cheers.

PS. I'd be inclined to get the same screw for all throttles...

[911pcars]

I've run across these on the idle mixture screws as well. My theory is that the longer, tapered profile provides a finer adjustment of the air (or air/fuel) bleed; perhaps more prevalant in the early smog days. I think you should be okay as long as you monitor the idle air flow with an airflow synchronizer of some sort (e.g. Unisyn) despite the taper difference.

Sherwood Lee
http://members.rennlist.org/911pcars

[cegerer]

I can't see leaving an oddball in there if you're going thru the expense of rebuilding anyway. While you can probably adjust it to make it run right, why not make them all the same. Mine are all the same and I'm sure that's the way they come. Air correction screws are only $5 a piece.