Weber Tuning Question

[avendlerdp]

I have a set of weber 40's on my 70t. Runs well but a bit lumpy at idle. I have the carbs synced up fine but I noticed that the bypass compensators are all cylinders turned out about 1.5 turns. I thought they are supposed to be closed normally and only opened to make a "slow" cylinder match up wih the rest of the bunch. Should I close them all and start over? Thanks, Alex P.S. What size bulk spark plug wire are you fellows using on your cars?

[Early_S_Man]

Alex,

Those aren't 'bypass' screws ... they control ALL of the fuel flow from the idle jets! The 'normal' setting is 1-1/2 to 1-3/4 turns out, so yours sound fine!

I use 7 mm silicone spark plug wire with a stainless steel core ... AC Delco SS-550, with stock connectors on both ends, and check the air seals frequently in the summertime for warpage that would cause cooling air leaks!

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Warren Hall
1973 911S Targa

[avendlerdp]

I am referring to the OTHER adjustment screws on the side of the barrels. One set are for fuel and have springs to keep from turning. The ones I am talking about are held in place by a locknut. They are air bypasses... Alex

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[BRAINIAC]

Then yes, those are the air bypass screws and should be turned all the way in except to compensate for less flow than other cylinders. Start by screwing all of them in. Then only back out the ones you need to to get them all in sync. You use the bypass screws to sync. individual carb only. To sync right bank to left bank, you use the idle stop screws. Then when all that is done you adjust the throttle drop links so left and right carbs lift off the stop screws at the exact same time.

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet