Installing Twin Weber 40IDA 3C Carbs
04-24-2004, 07:41 PM
#1
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Installing Twin Weber 40IDA 3C Carbs
I am planning to convert my 1981 911 SC from the current CIS fuel injection to twin weber 40IDA 3C which I bought on eBay and came off a 1980 911 SC. My plan is to remove the CIS as one piece, use intake manifold insulators, install the manifold and carbs, hook up the fuel lines using a fuel regulator set to 3.5 lbs per
sq inch, install 2 fuel filters, and then set cards with a syncrometer. Though some people have advised me to have the distributor recurved, I plan to go without it and seeing how it does. Am I forgetting anything? Any advice? Any thoughts or ideas would be appreciated. I don't want to screw it up.
sq inch, install 2 fuel filters, and then set cards with a syncrometer. Though some people have advised me to have the distributor recurved, I plan to go without it and seeing how it does. Am I forgetting anything? Any advice? Any thoughts or ideas would be appreciated. I don't want to screw it up.
04-25-2004, 05:11 AM
#2
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Hi:
I would install everything as you said and simply set your timing at 35-36 deg total at 6K with no vacuum advance.
See how it drives for you. As long as you are in the 10 deg ballpark at idle, you'll be just fine.
I would install everything as you said and simply set your timing at 35-36 deg total at 6K with no vacuum advance.
See how it drives for you. As long as you are in the 10 deg ballpark at idle, you'll be just fine.
05-04-2004, 01:04 AM
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recurving the distributor allows the advance profile to be optimized specifically for the carb set up.Getting these cars to run their best is in the details.You don`t have to do it but taking the time to properly jet the carbs and optimizing the ignition functions will make a real difference.You`ll feel it right away and you won`t have to be tweaking it all the time to make an unbalanced conversion run right.
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05-04-2004, 10:25 AM
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Still does not specifically answer the question. Why specifically does the firing of the spark plugs need to be different for the carbs compared to the CIS? Does it require more advance b/c the fuel is slower going into the cyclinders, does it need more retard b/c the mixture takes longer to mix well, does the mixture have more droplets and thus the spark needs to be later to allow a stronger spark to build, what exactly is the reason?
