Weber 40IDS

[Joe901]

I have just bought a set of old IDS carbs.

They have come to me in plastic bags completely dismantled and with some missing parts.

The most serious parts that are missing ar 4 of the 6 booster Jets



I relasise that these parts will be hard to find but is is possible to run these carbs without them being fitted?

Can I just leave them out? and jet tham as per the early 40IDA3c spec with 135 main jets or do I have to block the galleries that allow fuel to them?

[Cliff]

http://www.performanceoriented.com/ This will be a good source for sure....Cliff

[1QuickS]

Hard to find indeed, I have no spares. OK to run without, definitely. They have exactly the same progression circuit and idle air bleeds of the IDAs and the remainder of the bits are interchangeable. It would be good to plug the hole in the top of the main throttle body that feeds them. The earliest 2.0 911S engines used IDA carbs that were stamped with an "S" to identify their unique jetting which was: 32mm venturis, 135 mains, 170 air correction jets, F26 emulsion tubes and 55 idle jets. The IDS carbs were the same except they used 125 mains, 185 air corrections and F3 E-tubes.

I have a customer who vintage races a 914/6 with dyno work showing there to be an advantage in high RPM HP but street applications don't need them in my opinion. Best guess is they were used to help enrich during sustained high speed cruising (Autobahn) to avoid piston melting.

Note that they were not offered for after market sales by Weber after the carburetted 911Ss were no longer in production.

[Joe901]

I had pretty much given up the idea of finding spares and have the early Volume 1 manual and had observed the jetting differences - I will take your valuabale advice and will block the 'feed' holes to avoid potential issues.

I agree that they were used for 'high' speed Autobahn work and I think period races used to remove them as they were not always totally reliable.

I wounder it there is the same issue with the Solex 40PI enrichement circuit?