It’s really going to depend on the carburator you’re going to be using. For me as a general rule I like a 650CFM on engines of around 350 CI and a 750 CFM on engines 400CI and above. The 383 falls right in between and I have had good luck with both 650s and 750s on them…….but…..it depends in large part on how the car is driven and most importantly the style of carburator.

As mentioned the CFM rating is based on WOT and unless it’s a race car 98% of your driving is going to be on just the front 2 barrels. Generally speaking on a street engine you want to stay away from the mechanical linkage “double pumper” type carbs for a street engine.

You will want a vacuum secondary carb like Dave suggests, something with an air door over the secondary’s like the Quadrajets, Thermoquads and Carter AVS clones, or one with an internal air valve like the Carter (and clone) AFBs. On these carbs, when properly tuned the amount of air/fuel is limited to what the engine can handle regardless of what the total CFM rating is.

There are possibly going to be 2 issues you will have to deal with on either the 650 or 750 on a 383. The first is jetting; most out of the box aftermarket 650 CFM carbs are jetted for a relatively stock 350 at sea level and most 750CFM carbs will be jetted for something with around 450 CIs at sea level. The second issue is primary throttle plate size. The bigger the throttle plates and venturi the less vacuum signal the carb sees and on smaller engines the less responsive the engine will be at low and part throttle RPM. The spread bore carbs (Quadrajet and Thermoquad) have very small primary throttle bores and huge secondarys (with a spring loaded air door) allowing for good throttle response and CFM ratings starting at 750CFM and in some cases going clear up 1000CFM.

If it was me………scratch that….. because if it was really ME I’d throw dual quads or Tri-Power on it

I’d recommend a 650 Vacuum secondary Holley, a 650 AFB or a rejetted Quadrajet from a 350 if you’re just going to be cruising the car. If you’re going to be playing with it I’d jump up to a 750 VS Holley, 750 AFB (possibly AVS, but I think you will find the primary throttle bores a bit big) or again a Quadrajet.

Just my 2 cents.


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