Weber Carburetor conquerers please help !

Guys,

Let me start by saying I recently went through the process of completely rebuilding(soup to nuts) my Weber 40 IDA3C carbs.

All jet and venturi sizes are correct as the car was a SC/Carrera-wrecking machine before it was stored some 10 years ago. The car runs decent but not like the Rolex it once was. It's an easy starter and all the obvious set-up work has been addressed(fuel pump, 3.5 lbs. pressure. the correct plugs, correct distributor, etc.). Here's the question:

What are some possible culprits for my inability(regardless of air comp. adjustment, idle mix.adj., and throtttle position adj.) to get one carb. to intake as much air as the other? On the Unisyn, the drivers side carb has an air intake reading of 2(out of 3) while the pass. side carb. won't intake more than 1(out of 3) on the Unisyn(regardless of tweaking). Any help would be appreciated. Thanks in advance.

Rich

Let me see if I understand this situation ... you can adjust all three circuits on the left carburetor to the SAME flow, exactly, and that turns out to be midway, or 2nd mark on the Uni-Syn, but none of the right carb. circuits can be adjusted close to 2, but all three can be 'sync'ed' to flow at '1' ???

One suggestion: when using the Uni-Syn next time, dial the center 'restriction' in so your 'max' flow rate is showing right at, or just under the 3rd, or top mark, making it most 'sensitive' to fluctuations. One possibility is a warped right carburetor base, or throttle body, for lack of a better term, and I think you should carefully remove it and check with a machinist's rule, or perhaps the machined table of a drill press. Another, more likely problem would be a leak at either the cylinder head-manifold juction, or manifold-carb. junction, due to cracked, old gaskets. If you replaced the manifold-head gasket at rebuild time it just gets 'curiouser & curiouser' ... to say the least! Of course, a warped, or cracked manifold is a remote possibility, too, which you should check for! One final, extremely remote possibility ... is it possible there are different venturi sizes installed in the two carbs, say, 35 mm in the left carb. and 30 mm or 32 mm in the right carb? Strange problem generates strange ideas! My basic thinking is that there has to be a mechanical leak on the right bank, somewhere, causing slightly less vacuum and flow through the carb, compared to the left carb.

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Warren Hall
1973 911S Targa

Warren,

Thanks for the input. The air leakdown may be a culprit although I did replace all gaskets with quality PMO rebuilds. I'll let you know. Any other input would be appreciated.

Bruce Andersen replied to me and stated it may have something to do with the linkage to balance the carburetors from side to side.

Any other thoughts please forward. Thanks guys.

Rich

One hint make sure you adjust the carbs with the linkage Completely disconnected, for there will be no pull on either side.

Roy at http://www.motormeister.com