Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)
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Old 03-01-2011, 01:01 PM
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lt1silverhawk lt1silverhawk is offline
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Hey Guys,

Sorry that I haven't posted anything. I was away for a week, spent the last week reading Ruggles' book, and this week I'm laid up in bed with the flu.




Quote:
Originally Posted by cobalt327
The subject of leaking wells on the Q-jet and what to do about it comes up fairly often.
In the book, Cliff says: "Simply dabbing epoxy over the leaking plugs does not work as a long term repair. The epoxy eventually comes loose from the aluminum after many heating-up and cooling-down cycles of the engine." (chapter 5, page 71). I of course, have done just that as a precaution since the wells aren't suspected of leaking.

In addition, the book also mentions a leak test for the plugs: "Apply a soap-and-water mixture over the plugs, then introduce high-pressure compressed air in through the front and rear jet openings in the fuel bowl. A small leak shows a tiny stream of bubbles. Large leaks ... are easy to detect!" (chapter 5, page 71).




I did email Cliff regarding the power piston retainer and he sells it as a part of a rebuild kit. Had I not already bought one, I would have ordered his. I will give him a call to see if he sells it individually (the email made no mention of it). If not, I'll order it from Quadrajetparts.com. In the book, Cliff mentions that the power piston retainer can be held down "with a machinist's ruler during carburetor assembly. (chapter 5, page 84).




While reading the book, I realized one of the things I didn't check for was warpage. I had taken some pictures this past weekend of the carburetor as it sits. It seems like there is a gap between the air horn and the fuel bowl in the rear of the carb. The book says this can be fixed using a belt sander (chapter 4, page 68). Anyone feel this carburetor needs to be sanded or is it negligible?






I also made my way over to the "High Performance Modifications" chapter. My rig is in no way setup for high performance nor do I have any such plans for it. But the book does mention that these mods help "improve performance, driveability and fuel economy." (chapter 6, page 88).

One of the mods mentioned is making sure the throttle plates open up a full 90 degrees. Here are pictures of my carb and the secondaries are opening almost 90 degrees. Sufficient enough?





Another mod listed for throttle plates is drilling small holes in them to add additional air at idle. It is mentioned as an alternative to another mod, which is adding an idle bypass air system. But these are not necessary if the idle bypass air system is already in place. (chapter 6, page 95). I need to check to see if this carb has this system already. If not, I may just drill the plates since adding the idle bypass air system requires alot more work and precision.



**All quotes and cited sections are from Cliff Ruggles' "How to Rebuild and Modify Rochester Quadrajet Carburetors", copyright 2006.

Last edited by lt1silverhawk; 03-01-2011 at 01:22 PM. Reason: More info added.
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