screws snapped off in the secondary throttle shaft of my rochester quadrajet - HELP! - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-19-2012, 08:35 PM
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screws snapped off in the secondary throttle shaft of my rochester quadrajet - HELP!

So I am disassembling my 78 rochester quadrajet, and when removing the secondary throttle shaft screws to remove the butterfly, even being gentle, I snapped off the screw head. Same with the other one.
SO, i tried to back them out with a screw tap kit, no luck. So I drilled it out, but had to drill it a little bigger. My questions are these: do I need to drill out the other side, for balance? Is the extra weight of bigger screws going to mess with the opening of the secondaries? Any other foreseen issues? I have no idea how delicate the balance is with weight in these throttle shafts. Also, the re-bushing kit is $79, and I cant even find a secondary throttle shaft out there for sale. Kinda stuck, please help!
Zak

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Old 02-19-2012, 09:25 PM
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Quote:
Originally Posted by JMSTOY
So I am disassembling my 78 rochester quadrajet, and when removing the secondary throttle shaft screws to remove the butterfly, even being gentle, I snapped off the screw head. Same with the other one.
SO, i tried to back them out with a screw tap kit, no luck. So I drilled it out, but had to drill it a little bigger. My questions are these: do I need to drill out the other side, for balance? Is the extra weight of bigger screws going to mess with the opening of the secondaries? Any other foreseen issues? I have no idea how delicate the balance is with weight in these throttle shafts. Also, the re-bushing kit is $79, and I cant even find a secondary throttle shaft out there for sale. Kinda stuck, please help!
Zak
First, the ends of the original screws have to be ground away because they're "staked" at the factory. You may now have noticed this- the ends are split a slight amount to make them impossible to loosen and back out and fall into the intake.

There's absolutely no need to worry about matching the two sides screw sizes. Just use the next larger size and use loctite as well as "peening" the ends of the screws.

To do the peening, I clamp a piece of square stock into a vice to use to set the screw head on, and peen the ends of the screws over w/a small jeweler's hammer or ball peen. You don't need to simulate the factory way of staking, the main idea is to disrupt the threads on the end of the screw so they cannot fall into the engine. The loctite will do the rest.

If the ends of the screws look too long, they can be ground down w/a dremel to the approximate length of the stock screws before peening them.

Be very careful if you end up trying to find a replacement for the secondary shaft. They are not all the same. I'm curious. Why did you remove the shaft if you aren't bushing it?
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Old 02-20-2012, 06:55 AM
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I'm not removing the shaft, just the butterfly's. They were literally "gunked" shut with what looks like mineral deposits. Could have been from sitting at my shop for a while. Regardless, I took off the butterflys to wire brush that crap out. Now that the secondaries are opening again, I'm going to start reassembling. Thanks for the info! I was a little worried!
Zak
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Old 03-24-2012, 03:09 PM
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Quick follow up. Finding screws that size was no prob, but I had to drill it out, so of course bigger hole. So I just measure, went up one thread size from the measurement, and drilled and tapped the hole. Make sure if you are doing this, that you can find a readily available combo of machine screw and drill and tap set that match. I bumped up the thread size by one because I couldn't find anything the right size except expensive online special size. Duh! So I went to the hardware store, found the next size screw, walked over two aisles and found the matching drill and tap combo. Seems easy but I got tunnel vision trying to fix my mistake. Anywho, works like a charm now.
Zak
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