Less than two weeks ago I pulled the 302 from my 65 Fastback and replaced it with a 347 from Blue Print Engines. I moved the manifold and Webers (IDF 48) over from the 302 without any initial change to jetting. I did re-sync the carbs and made sure the linkage was functioning correctly. After getting the timing set to 34 degrees at 2500 RPM (mechanical advance distributor) I noticed a bit of popping between 1000 and 2000 RPM. Switched the idle jets from 60's to 70's but don't see much difference. Thinking I probably need to look into larger main jets and perhaps emulsion tubes. Currently I have 160 Main jets and F11 emulsion tubes.
Does anyone know of any sort of a cheat sheet for predicting what jets might be needed for Weber carbs? I am thinking these can be run singly, in pairs, in threes or in my case in a set of four. Most manifolds have a shared plenum of some sort so you would have to factor the total CI/CC displacement serviced. Often in the case of one carb there is a plenum that distributes the mix across all cylinders, with dual carbs perhaps there is a plenum for one side of the motor and another (with the other carb) servicing the other side. With three there is generally a common plenum that service all cylinders.
In my case I have four carbs with one half of each carb servicing one Individual Throttle Bore (ITB) on the manifold. I have a 347 Stroker so divided by 8 each ITB is serving about 44 CI or 721 CC. There are a couple of charts in the Weber Tuning Manual but I am left with questions looking at those.....
Does anyone know of any sort of a cheat sheet for predicting what jets might be needed for Weber carbs? I am thinking these can be run singly, in pairs, in threes or in my case in a set of four. Most manifolds have a shared plenum of some sort so you would have to factor the total CI/CC displacement serviced. Often in the case of one carb there is a plenum that distributes the mix across all cylinders, with dual carbs perhaps there is a plenum for one side of the motor and another (with the other carb) servicing the other side. With three there is generally a common plenum that service all cylinders.
In my case I have four carbs with one half of each carb servicing one Individual Throttle Bore (ITB) on the manifold. I have a 347 Stroker so divided by 8 each ITB is serving about 44 CI or 721 CC. There are a couple of charts in the Weber Tuning Manual but I am left with questions looking at those.....
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