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!
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?