How to rebuild a Rochester Quadrajet 4MV carburetor
(→Throttle shaft bore wear) |
(Minor clean up; add text) |
||
| Line 213: | Line 213: | ||
=====Leaking float bowl well plugs===== | =====Leaking float bowl well plugs===== | ||
| − | A common problem on the early Q-jets especially, is leaky main wells. The 'cure' for this has long been to use JB Weld, etc. to seal them over. This is just a stop-gap measure, | + | A common problem on the early (1968-back) Q-jets especially, is leaky main wells. The early leak-prone plugs can be identified by being brass cup-type plugs as opposed to aluminum. The late-type plugs are shown below, left- front plugs arrows, rear plugs circled. The 'cure' for this has long been to use JB Weld, etc. to seal them over. This is just a stop-gap measure, the epoxy will degrade and quit sealing. |
| − | + | ||
| − | + | The well plug stop-leak pads that come in many rebuild kits are a joke (below, right). They will seal the leaking rear plugs for a few heat cycles before shrinking down to a fraction of their former thickness. The result is the carb will initially run as it should, ''quickly'' followed by the same symptoms of a leaky plug returning. Do not waste your time with them. If you have a leaking plug, repair it right. | |
| − | + | ||
| − | + | [[File:Q jet well plugs.jpg]][[File:WELL PLUG 1.jpg]] | |
| − | + | ||
| + | FWIW, there is an epoxy by Devcon (made in the USA, look for "Devcon Home"). It comes in the older 2 tube packages and the newer double plunger syringe type. On the back it clearly states it <u>*RESISTS UNLEADED FUEL*</u>, salt, gasoline, oil etc. Full set time 8-12 hrs/2500 psi. However, be aware there is no empirical evidence that this epoxy will work for the life of the carb without any delamination or degradation. Ruggles also mentions using Marine Tex epoxy to seal the threads of replacement well plugs, but he states that using epoxy alone to repair a leaking well plug is akin to "cutting your arm off and putting a Band-Aid on it". | ||
| + | |||
| + | So, if a '''''permanent''''' fix is wanted, the wells can be resealed with new plugs that are peened over to hold them in place, or the wells can be drilled and tapped for plugs that will seal them for good. The primary wells seldom leak, the secondary wells on the early (1968-back) carbs do leak much more often than the later carbs. | ||
Also please see post #48 on [http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-4.html page 4] on the thread [http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558.html ''"Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level")''] | Also please see post #48 on [http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-4.html page 4] on the thread [http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558.html ''"Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level")''] | ||
| Line 235: | Line 238: | ||
[[File:Throttle return bad.jpg|thumb|800px|left|Bad throttle return spring orientation]] <br style="clear:both"/> | [[File:Throttle return bad.jpg|thumb|800px|left|Bad throttle return spring orientation]] <br style="clear:both"/> | ||
| − | + | =====No drilling/Teflon bushing fix===== | |
| − | + | [http://67-72chevytrucks.com/vboard/showthread.php?p=4688535 No Drilling / Teflon Bushing Article] shows how to re-bush the primary shaft with no drilling by cutting a teflon sheet into small strips, as shown below. The teflon sheets are available from smallparts.com as well as many other sources online. If this is attempted, be sure that the amount of wear is measured so the right thickness of teflon sheet is used. | |
| − | + | ||
| − | + | [[File:QJet 3.jpg|500px]][[File:Teflon_bushing.jpeg|530px]] | |
| − | [[File:QJet 3.jpg]] | + | |
| − | [[File:Teflon_bushing.jpeg]] | + | |
| − | + | ||
| − | + | This fix leaves the body original, however a correctly done repair will not detract from the value of a carb in most cases, in fact it adds to it due to the permanent nature of fixing it with a brass/oilite-type bushing as opposed to using a material like teflon that will wear out much sooner than a bushing. | |
=====Throttle blade screw removal===== | =====Throttle blade screw removal===== | ||
Your Privacy Choices