Reamers for bushing throttle shaft.

Back in my dark days as a line mechanic I used to do that process. I was cornered into it because of on my VW's the spring return side of the carb body would wear out and cause a vacuum leak. This would cause all kinds of mayhem with the idle mix and actually in running as this was unmetered air making one side of the engine(cyls 3&4) run leaner and even hotter. Making an already bad situation even worse. One day a salesman for an outfit that sold the "kit" for installing brass bushings came through and I bought the kit. It had nothing for actually aligning and drilling the holes. I ended up making a jig out of some 6x6 precision ground aluminum angle as the base and one of those drill guides. I used a reamer of the original size of the shaft to set up the carb body and drill guide and clamped the carb and guide. Then drilled the body. Installed the bushing and then ream to size. The other tricky thing is to remove the butterfly. Removing the screws without destroying the shaft is a trick. I used brass screws to replace the old ones and then peen them in so they don't vibrate loose. After it worked so good with my old VW I started doing QuadraJunk's so they could pass smog and got to where the Chevy garage came to me to fix their QJ's.
 
with that setup you ream the hole, pound in the bushing and you're done
 
I've only done a few, but they all had worn shafts, that necessitated making new ones or replacing them with stock ones.

Greg
 
cg285 said:
this is the quadrajet tool. it has a long pilot and a depth stop

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That would have been a nice rig, but that isn't what the kit was. I think the name of the outfit was WinCo? The reamers I have all have the guide nose on them that I don't see on machinist reamers. I went to find my old rig but it all had been repurposed. I bailed on the biz in '88 so it's been a while :). The kits I see online are $200! I guess it's with that special reamer there. It will be interesting to see how the OP does because if I remember the carb correctly it has this insane multi linkage from the carb body to top.
 
chips&more said:
Is this enough wear to cause a vacuum leak that will effect engine performance? If you want to do something about it no matter. I would just lathe out to size (ID & OD) the brass bushings. Leave the shaft alone. Yes, it will not be perfect. But will be better…Dave
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C-Bag said:
I started doing QuadraJunk's so they could pass smog and got to where the Chevy garage came to me to fix their QJ's.
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I have a question- just how tight was the throttle shaft to body when new? Who has THAT number? There is no lube, other than gasoline and dirt!
What I am saying, is this- If the shaft- to- body clearance has worn to the point it has become a detriment to driveability, then ANY reduction in that wear will improve driveability. As soon as you come off idle, what is the path of least resistance for airflow? If you make it TOO tight, that will surely affect driveability!
I am a bit of a QuadraJet fanatic. I have them on my Ford 302, my Ford 460, and my Mopar 440. I have built several, over many years, for fun and profit. The throttle shaft measures .308 inches. Do we have any reloaders reading this? You take the neck off a fired 30-30 Winchester case (Because it is LONGER than other 30 cal case necks), drill your carb throttle plate somewhat larger (no precision tooling required) than the brass OD, slather the holes with JB Weld, stuff the brass and shaft thru. The throttle shaft will align the brass, the brass will settle straight because of the JB, and then fit your butterflies after the JB sets up. The toughest part of the whole job is removing the screws holding the butterflies to the shaft, and finding their replacements. The improvement in idle quality (which is the only thing this whole thread is concerned with) will be dramatic. At any flow beyond idle, the wear between throttle shaft and body becomes entirely insignificant.
 
Right now the engine dies when the clutch is disengaged and the accelerator is not pressed - it dies at idle.
Unworn portions of this throttle shaft are .3085 If I use 5/16 (.3125) bushings then I'll be making the fit a little better.
I don't have a Winchester case.
MH22nd says that an RC1 fit is .2 to .6 thousandths clearance.
The smallest boring bar I have will just fit in a .339 hole.
I guess no one makes a .309 reamer nor a 7.86 mm reamer.
I'm thinking of looking for a used carburetor at a wrecking yard.
 
Perhaps turn some O1 steel or similar to the appropriate dimensions and make a D-bit reamer? Might not even require hardening assuming the carb body is aluminium or similar material and it being a once and done type task.
 
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I have half a dozen 3/8" nominal chucking reamers with 5/16" shanks. The reamer sizes are actually from .374 to .3755", and not all of them are as sharp as I would like... I was not overly impressed with the idea of using the reamer backwards. No taper to start the hole concentrically, and all the loading on the sharp corners of the flutes. I think it would tend to make oversize holes with a rough bore that is off center. A sharp piloted reamer with a tapered entry would be the best bet for keeping the holes centered, to size, and with a smooth surface. Actually, something like a scaled down king pin reamer set would probably be about ideal.
 
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