Webers

[911split]

What are the differences between Weber 40mm 3C-1 IDA, IDS, and IDT carbs? I'm looking to add Webers to a 3.0SC engine and like the look of the vintage Webers.

I've heard that PMO's may be superior, but what about among early Webers? Is there a preferred carb? And, can the early Webers actually be updated to perform identical to the PMO's?

Thank you,
John

[ttweed]

I believe the IDA and IDTs are the same except for configuration- jetting and venturis to match the engine spec, but not positive, having never held any IDTs in my hands and really examined them. The IDS model is the same body but with an extra high speed enrichment circuit for above 4500 RPM. I believe you can have the IDAs converted to IDS by Bieker Engineering and others. The IDS is preferred by racers, but it is not clear that the extra enrichment improves performance.

The PMOs are superior to the Weber design in several ways, solving the percolation and float bowl slosh problems the Webers had, but you can modify the Webers to fix these problems. The one thing you get with the PMOs that cannot be retrofitted to a Weber easily is a float bowl sight glass, which is a big improvement. A float level gauge does not have to be hooked up to a PMO to see what the level is, there is a window to visually check the level in each chamber. This is a huge improvement for tuning them. Also PMOs improved the throttle shaft sealing by putting bearings at the butterfly pivots, but an older set of Webers can be rebushed, it is just an expensive operation.

TT

[911split]

Great information! Now i can make my decision.

Thank you.