Difference in Weber Carbs?
 

I see three types of webers advertised consistently. The 40 IDA, IDT and IDS. What is the difference and which are the most desirable? I have a 1970 911T that I would like to buy a set of webers for. I own both of your books but have not been able to find the answer.
Thanks in advance,
Christian

AFIK, there is not much difference betwen the IDA and the IDT other than jetting. The IDS was offered in the early (67-68?) 911s with a high speed enrichment circuit.

They can all be rejetted for your 70T. Just make sure you find a clean set with tight throttle shafts. you do not need to buy a complete set since the manifolds and linkage from your (assuming) Zeniths will work.

One thing I've noticed in the IDT carbs is that, for emissions, the profile of the idle mixture screws are different. A more normal profile would be a smooth taper to a point. The IDT mixture screws had less slope to them - more needle-like. The end result is less adjustment of the idle passage orifice size as the screw threads in or out. I replaced with IDA/IDS-type mixture screws.

Sherwood