Carb size help

boosted68stang said:

I called there tech support to ask what size they recomended and they said around 600-650cfm does this sound about right?

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It sounds right for the size of your engine. The thing that I'm not sure about is the fact you're using a supercharger. Since you're pumping more air into the engine I'm thinking you might need a bigger carb to mix the right amount of fuel with the additional air you're pumping in the engine. But I'm not totally sure about that, so don't take my word as gospel. Someone with supercharger experience needs to chime in and give some advice. But for a naturally aspirated engine, the 600 to 650 carb is perfect; that I do know for sure. Another thing I know for sure is that you can over carburate your engine, which will hurt performance so don't go too big. Bigger is not always better when it comes to carbs. Getting the correct air/fuel ratio is your goal because that will determine how well your engine performs. If you go too big of a carb, you're gonna be running way too rich, which will kill your performance.

347 + boost.... and a 600-650 BT carburetor is OK? A little history regarding the "over carbed" stuff...... '65-'66 Shelby 289 ci GT350's came with a 715 CFM Holley...... the 1969 302 Boss had a 780 CFM Holley.... and a 750/825 on a SC 347 setup could be over carbed?...

A carburetor is a passive device, it depends/reacts to the engine demands IOW..... you can place an 850 DP Holley on a 289 and tune it correctly for street use... BTSTDT moooons ago. For your SC 347 it's better to "err" on the rich side (if you feel a little worried), since forced induction and a lean condition would be a little dangerous for the health of that engine.

boosted68stang said:

so how much cfm would you recomend? I was looking into 750cfm but like you said I much rather put a bigger carb on then a to small of one to run lean I just dont want overkill either

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Since you're going to get alot of varying opinions on here, maybe you should call a Edelbrock, Holley or any other carb company and ask them what they recommend. Since they make the carbs I'm sure they would know what size carb would be best for your engine setup....But no matter what others say, it is possible to over carb your engine. A carb company will tell you the same thing.