I think I need to go to Carter BBD Skool !

[MOPAROFFICIAL]

The standard practice is to ream out the base plate and install bronze bushings. There are 2 things against this. Not enough room in the base plate to ream it out, and nobody makes bushings to do so.

And yes, you can make bushings. But at some point, there is diminishing returns on the costs involved. And just how NOS was that carburetor? NOS can mean that the carburetor had bad throttle shafts and was replaced with something better. And somebody just picked it up out of the discard pile and sold it online.

The BBD has always had this problem, that is why it was a great carburetor 50 years ago, not so much now.

Machine shaft for o rings...and or the base plate in conjunction with an end cap.
It probably is only going to help idle and that's about it. Once the throttle plates open...the restriction is the shaft leak and it won't pull any air from it at that point.

 

[Slantsix64]

Run less timing, 5-8 btdc is a good spot.

 

[volaredon]

The 2 NOS BBDs I bought last year were still in the factory plastic wrap.
I have used 1 so far and it was absolutely fantastic
I have the 2nd one out of the plastic and on the engine it will be used on but not yet bolted down or linkage hooked up either.
There was a guy on the /6 site that had like 10 of these a little bit over a year ago and sold them out quickly. Not chunesium reproduction but actual honest to goodness brand new Carter BBDs from around 1978. All were carb number 6537, which comes back as a 318 application from 76-78-ish 318 "HD truck" application (back then "HD emissions" basically meant "no" emissions gizmos besides a PCV valve.

 

[Duggie]

Run less timing, 5-8 btdc is a good spot.

That I can do while waiting to go see the other carb guru. The one that did the original work got pissed when I told him I had a vacuum leak.

Sometimes people are funny in not so funny ways.