How to rebuild a Rochester Quadrajet 4MV carburetor
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(Section on warpage and linkages added. Updated section on Power Piston Retainer. Added note on taking good photographs of linkages before disassembly. Minor clean up, reorganization and editing.) |
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'''''Note:''''' Be sure to have your parts organizer near by at all times. Also, take the time to match up the new parts with the old ones as soon as you remove them. If something doesn't match up, return it for the right part before beginning re-assembly. | '''''Note:''''' Be sure to have your parts organizer near by at all times. Also, take the time to match up the new parts with the old ones as soon as you remove them. If something doesn't match up, return it for the right part before beginning re-assembly. | ||
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====Choke and Linkage==== | ====Choke and Linkage==== | ||
| + | '''''Cautionary Note:''''' It is very important to take good, well-lit, close-up pictures of the linkages before dis-assembly. The choke linkage has several parts that must line up in a specific way during re-assembly or they will not work. | ||
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''Coming soon.'' | ''Coming soon.'' | ||
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====Air Horn and Metering Rods==== | ====Air Horn and Metering Rods==== | ||
''Coming soon.'' | ''Coming soon.'' | ||
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*Jets | *Jets | ||
*Fuel Filter Housing | *Fuel Filter Housing | ||
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*Idle mixture screws | *Idle mixture screws | ||
*Gasket | *Gasket | ||
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=====Loose Power Piston Retainer Cap===== | =====Loose Power Piston Retainer Cap===== | ||
| − | According to | + | According to Hotrodders forum member '''''TommyK''''': |
<blockquote>''"It is not uncommon for the retainer to fail to positively secure the PP in its hole in and of itself. The solution is to take a chisel and gently stake the edge of the hole in one or two spots against the retainer." ^''</blockquote> | <blockquote>''"It is not uncommon for the retainer to fail to positively secure the PP in its hole in and of itself. The solution is to take a chisel and gently stake the edge of the hole in one or two spots against the retainer." ^''</blockquote> | ||
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| + | According to Hotrodders forum member '''''cobalt327''''': | ||
| + | <blockquote>''"Just be sure that when it's all said and done that there's positively no friction from the retainer on the PP shaft itself. It has to be absolutely free to move w/o any hindrance."''</blockquote> | ||
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=====Worn Shaft Bushings===== | =====Worn Shaft Bushings===== | ||
| − | According to | + | According to Hotrodders forum member '''''cobalt327''''': |
<blockquote>''Usually the play will be on the primary shaft. The shaft is teflon coated (that green colored material) but despite this, the shaft wears directly on the aluminum of the throttle plate. There are bushing kits to fix this if it's worn too much.</blockquote> | <blockquote>''Usually the play will be on the primary shaft. The shaft is teflon coated (that green colored material) but despite this, the shaft wears directly on the aluminum of the throttle plate. There are bushing kits to fix this if it's worn too much.</blockquote> | ||
<blockquote>''How much is too much? If you get an erratic idle or if it's obviously worn out. There will be play in ALL of them, though and that's where determining how much is too much is tricky. But if it idles good, it's good to go, IMO." ^''</blockquote> | <blockquote>''How much is too much? If you get an erratic idle or if it's obviously worn out. There will be play in ALL of them, though and that's where determining how much is too much is tricky. But if it idles good, it's good to go, IMO." ^''</blockquote> | ||
| − | According to | + | According to Hotrodders forum member '''''willys36@aol.com''''': |
| − | Worn throttle shafts are self inflicted. To avoid premature wear on any carburetor, set up the throttle return spring as shown in the 'Best Case' in this picture | + | <blockquote>''Worn throttle shafts are self inflicted. To avoid premature wear on any carburetor, set up the throttle return spring as shown in the 'Best Case' in this picture: [http://www.hotrodders.com/gallery/data/500/2439throttle.jpg Click here for image].''</blockquote> |
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=====Cleaning Float Bowl Orifices===== | =====Cleaning Float Bowl Orifices===== | ||
Please see posts numbers 23 through 28 on page 2 in the thread ''[http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-2.html Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)]''. | Please see posts numbers 23 through 28 on page 2 in the thread ''[http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-2.html Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)]''. | ||
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=====Throttle Blades===== | =====Throttle Blades===== | ||
| − | According to | + | According to Hotrodders forum member '''''cobalt327''''': |
<blockquote>''Check the base plate to be sure the throttle blades are exactly 90° when wide open. There are some who believe having the secondary throttle blades go "over center" helps w/A/F distribution w/some intakes. While this may be true, until you have a good grasp on the engine's tune and plug readings indicate a need for this, keep them @ 90°." ^''</blockquote> | <blockquote>''Check the base plate to be sure the throttle blades are exactly 90° when wide open. There are some who believe having the secondary throttle blades go "over center" helps w/A/F distribution w/some intakes. While this may be true, until you have a good grasp on the engine's tune and plug readings indicate a need for this, keep them @ 90°." ^''</blockquote> | ||
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| + | =====Airhorn Warpage===== | ||
| + | The warpage of the air horn is discussed in Ruggles' book. For additional discussion, please see posts 49 through 53 in the thread, ''[http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-4.html "Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)"]'' | ||
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'''Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''cobalt327''''': | '''Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''cobalt327''''': | ||
<blockquote>''"For some reason, I have found the base plate on many Q-jets to be missing a screw or two. While the base plate is "helped" being held on by the two long front bolts, it's still a good idea IMO to go ahead and add the missing screws. Just be sure to not over tighten these long bolts. If they're over tightened, it can warp the carb beyond use." ^''</blockquote> | <blockquote>''"For some reason, I have found the base plate on many Q-jets to be missing a screw or two. While the base plate is "helped" being held on by the two long front bolts, it's still a good idea IMO to go ahead and add the missing screws. Just be sure to not over tighten these long bolts. If they're over tightened, it can warp the carb beyond use." ^''</blockquote> | ||
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'''Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''cobalt327''''': | '''Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''cobalt327''''': | ||
<blockquote>''"There are a few tips and tricks, like placing a ~0.050" feeler behind the accelerator pump lever pin, so when you drive the pin towards the air horn lip it doesn't butt tightly against it- instead there's room to get a thin straight blade screwdriver in behind it to lever the pin back into position." ^''</blockquote> | <blockquote>''"There are a few tips and tricks, like placing a ~0.050" feeler behind the accelerator pump lever pin, so when you drive the pin towards the air horn lip it doesn't butt tightly against it- instead there's room to get a thin straight blade screwdriver in behind it to lever the pin back into position." ^''</blockquote> | ||
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''More Coming soon.'' | ''More Coming soon.'' | ||
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| + | =====Linkages===== | ||
| + | :*Choke linkage | ||
| + | ::Installing the ''"three hole"'' key will prove challenging. ''"Fishing"'' method works best. be sure that the accelerator pump has already been installed before installing the linkage and key. | ||
| + | :*Throttle linkage | ||
| + | ''More coming soon.'' | ||
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