How to rebuild a Rochester Quadrajet 4MV carburetor
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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. | 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 | + | =====Throttle blade screw replacement===== |
| + | As mentioned above, the screws can be enlarged to 6-32 if need be. The factory stakes the screws to retain them from falling into the engine, you should do the same. | ||
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| + | To do the staking, 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. | ||
If the ends of the screws look too long, they can be ground down with a dremel or small file to the approximate length of the stock screws before peening them. | If the ends of the screws look too long, they can be ground down with a dremel or small file to the approximate length of the stock screws before peening them. | ||
| − | The secondary throttle shaft | + | ====Secondary throttle shaft bushings==== |
| + | The secondary throttle shaft rarely ever need bushings; even brand new there's quite a bit of clearance between the shaft and throttle plate. If the secondary shaft/throttle plate bore so bad that bushings are needed, the rest of the carb is likely worn very badly; another core or at a least another throttle plate should be considered. | ||
=====Cleaning orifices===== | =====Cleaning orifices===== | ||
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