How to rebuild a Rochester Quadrajet 4MV carburetor
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If primary throttle shaft bushings are to be installed, the throttle shaft has to first be removed. After removing all the linkages and choke parts from the end of the shaft, the throttle blades will need to be removed. | If primary throttle shaft bushings are to be installed, the throttle shaft has to first be removed. After removing all the linkages and choke parts from the end of the shaft, the throttle blades will need to be removed. | ||
| − | First, the ends of the original screws have to be ground away because they're "staked" at the factory. You may notice the ends are split a slight amount to make them impossible to loosen, back out and fall into the intake. | + | First, the ends of the original screws have to be ground away because they're "staked" at the factory (see image below, left). You may notice the ends are split a slight amount or rounded over to make them impossible to loosen, back out and fall into the intake. All the screws that hold the throttle blades, air valve, and choke flap are staked in this manner. |
[[File:STAKED QJET SCREW.jpg|border|250px|left]] | [[File:STAKED QJET SCREW.jpg|border|250px|left]] | ||
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| + | Should a screw get broken off in the shaft, it can be removed by whatever method available; often drilling is done but be careful to get centered on the broken screw. A drill press is the way to do this best, with the throttle plate clamped down. There's no need to worry about matching the screw sizes side-to-side, in other words, if only one screw broke off, use the other original threaded hole along with the larger hole made for the broken screw. Just use the next larger size and use loctite as well as "peening" the ends of the screws. The original screw thread size is 3-48, however the holes can be opened up enough to use a larger screw like a 6-32 thread if need be. | ||
To do the peening, you can clamp a piece of square stock into a vice to use as an anvil to support the screw head on, then peen the ends of the screws with 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. | To do the peening, you can clamp a piece of square stock into a vice to use as an anvil to support the screw head on, then peen the ends of the screws with 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. | ||
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