Once the throttle shaft was free, I could feel a bit of play in it, which is a known source of vacuum leaks. As suggested by Reed on slantsix.org, I ordered a bushing kit from eBay. The kit has a reaming tool with a long shaft to align with other holes, so that the new bushing hole will be straight. However, the metal surrounding the hole is so thin that enlarging the hole would cut all the way through.
View attachment 1715616708
It's possible to add more metal (matv91 on slantsix.org showed
how to do it), but my propane torch wouldn't get the metal hot enough to melt an aluminum brazing rod. I took the throttle body into a machine shop at my workplace, and the machinist said the wear isn't really enough to worry about. On top of that, there's a fair amount of pitting on the throttle shaft itself, so I came to realize the seal is never going to be perfect and probably wouldn't be improved by installing a new bushing. That said, it might be good enough to run OK, if the rest of the carburetor works. If...
At that point I was considering just installing the carburetor to see what happens. However, a rebuild kit and a few other needed parts will add up to over $50. And there's no telling how well it would ever work. On the other hand, I can buy a brand-new Chinese replica BBD
on Amazon for $80. I'm going to try the replica.
The replica is set up for a 318, so I will need to use the choke bracket from the old carb in place of the one that will come on the replica (explained in Reed's Super Six article
here).
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