Quadrajet Throttle Bushing

[dougfather]

I'm planning on putting in bronze throttle shaft bushings for a qudrajet that I am rebuilding. I have access to a drill press and various drill bit sizes where I work. Anyway, I determined the shaft diameter to be 5/16" and the hole could be drilled to 7/16 (or slightly less).

Here is what I think i need:
http://www.mcmaster.com/#6391k165/=3nma1v

Anyway, does anyone have experience doing this and if so what do I need to watch out for?

 

[dougfather]

 

[85 Cutlass Brougham]

It looks like it might not work, but I am not sure as I have never done it. What I would do is measure the boss on the baseplate where the hole will be drilled. If it is smaller than 7/16, it won't work. If you don't have a vernier caliper, you can just use a 7/16 or 11mm open end wrench to get a ball park. From what I remember, the baseplate seems like it is thinner than 7/16 of an inch, so this bushing may be too big. I think the bushing is supposed to be pretty thin walled. I have a Quadrajet off a Cad 472 that has it's baseplate bushed, and it was a very thin bushing. I can't tell from looking if this bushing is small enough. There are complete kits available with the proper drill and bushings from companies like Jet. Remember that you need to drill all three holes in one shot or else you run the risk of getting the alignment wrong. So, the bit needs to be pretty long.

 

[DRIVEN]

I worked with a guy at a shop a few years ago that has a reamer made specifically for this purpose. The holes were drilled out with a standard bit first slightly undersized for the bushing. The reamer had a smaller size shank ( the same size as the bit) that was pulled 75% of the way through on both sides. The remaining 25% was left and used as a seat/shoulder for the new bushing. I used it on my own carb and it made a noticable difference. If you are using a standard drill or drill press be sure to go in straight or you may have binding issues. Good luck.

 

[dougfather]

It looks like 7/16 is too big. There isn't much metal especially on the "passenger" side of the carb.

 

[dougfather]

There are complete kits available with the proper drill and bushings from companies like Jet. Remember that you need to drill all three holes in one shot or else you run the risk of getting the alignment wrong. So, the bit needs to be pretty long.

I know those kits run anywhere from $50-60. I just wondered if they are worth it. Most of the ones I have seen include a drill bit, bushings, and loctite. Just wondered if anyone thinks these are the way to go.