carb for 383

[firebird77clone]

For my 350 stroked to 383:

The shop is saying the carb on it is no good. I've got a new 750, but I'm certain that's too big. I'm thinking a 600 or 650?

9:1 compression, long tube headers

Thanks in advance

[HOSS429]

it`s only 750 at wide open throttle .. i use them on everything from 289`s to 429`s ...

[rumrumm]

I use a 750 on my 383, and it is recommended for a lot of 383 builds. It depends a little on the kind of hp you are making, but if you are using it for performance, I would not use anything smaller than 700.

[Dave Severson]

If it's an automatic, I'd go with the trusty old 3310 vacuum secondary carb! Heck, I'd probably run the same thing if it was a manual shift! They're a good carb (the one's with the secondary jet plates are my favorites). Not terribly expensive and will hold a tune as well as any Holley.

[Mike P]

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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[firebird77clone]

Thanks all. I dropped the Edelbrock 750 on it, and it runs good. I think I have some fine tuning to do. Total advance is set to 35. Sounds a tad high to me. Shop only charged me $40 for the intake gasket change, is that a deal or what?

[36 sedan]

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

Now you're talking!!

[firebird77clone]

I'm having trouble with mid throttle. I found the timing tape I ordered many moons ago, cleaned the damper, stuck it on. Could barely read the #s behind the pointer. But, I think it was set somewhere around 35 total advance. I took a trip up a side road, adjusted the dizzy by seat of pants, got it better, but still a bit sloppy in part throttle. I'd love to give feedback on where the timing ended up, but the tape flew off! What is s goo source / economic model of timing light with dwell and tach?