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carburation or ignition?


Vehicle Information: Model: 911 T; Year: 1973; Body Type: Coupe; Engine (type, size, modifications): 2.7 liter (increased bore), E cams, Weber carburation; Total Mileage: 125000;

Hello,I've got a messy problem I hope you can help me wiht. I recently obtained a 1973 911T that has been in my family since 1977. My father installed the 2.7RS pistons/cylinders, 911 E cams and weber carburators. The car has been used for limited driving for most of its life.More recently it has been sitting. This finally lead to me getting the car. When I recieved the car it would not accelerate well. It would stumble and 'chuff' with quick throttle applies. I thought this endevour would be a good way to learn about mechanical engine management systems, having grown up with Electronic engine systems.I oringinally thought it could be the ignition timing. The car has the Bosch distributer with the vaccum advance plate welded to the base plate (the weber carbs having no vacume ports). This is my first question: What is a resonable ignition advance curve, and how to set the spring tension on the centrifigal advance mechanism to achieve that curve?After playing with the distributer I turned my attention to the carbs. I know that they have not been rebuild/cleaned for several years. I purchased rebuild kits for them and just finished reassembling them. I more recently tried to tune and synchronize them. I followed instructions from the weber manual and finally have the engine idling well and able to run to max rpm. BUT, quick acceleration will cause the stumble and chuff.I have the jet setting for the car, as follows:Weber 40 IDA 3CVenturi = 34Pre-atomiser = 4.5Main jet = 130Air correction jet = 175Emulsion tube = F26Idle metering jet = 50Pump jet = 50Please help! I've run out of ideas, and my wife is tire of me smelling like exhaust fumes!Nicholas Robinson

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