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Help! I am having my '72 Q-Jet rebuilt ('72 SS 402) and I know that the primary jets and possibly the secondary jets were replaced with oversized jets. Can anyone tell me what the proper size orifices are? I think this is a 650CFM carb. If there are slightly larger size jets that will perform nicely, pass this on also, but I would like to know what the stock sizes were so I can go back. Thanks in advance.
 

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Delco Rochester Carburetor Parts and Service Manual says:
Primary Jets - 7031977 (#77)
Primary Metering Rods (auto) - 7034849 (#49B)
Primary Metering Rods (manual) - 7034845 (#45B)
Secondary Metering Rods - 7045840 (CM)

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Fred Aldrich
The Chevelle Engineer
Web Site: www.CoreComm.net/~faldrich
 

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In '69 the Q'jet on the 396 and 427 ran the same primary metering rods but ran 7031971 primary jets. Six sizes smaller might account for the '71 and newer engines being so hard on gas. My 427 with 4:10 gears was close to the newer engines for gas mileage. The smaller jetting might work just fine for you.
 

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That setup with 77 jets is going to be pig rich unless the primary main air bleeds are just huge. Some are. start with that and work your way down, you'll get real good at popping the top off your Q-jet
 

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Keith & Tom's point is a good one. Double checked book and it says 77 but it could be a mis-print.

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Fred Aldrich
The Chevelle Engineer
Web Site: www.CoreComm.net/~faldrich

[This message has been edited by Fred Aldrich (edited 06-06-2001).]
 

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For reference, I run 71's and 41B's in my recently rebuilt '66 396 (now 408) with mild cam, stock exhaust and intake.

Yanked the plugs last night and they look a little too clean - may need to go to 72's or 3's. I believe the secondaries are AX's swinging from a K hanger.

Yea Tom, it's gotten to the point that I'm starting to look into buying the top gaskets in BULK!

Dan

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Awww, fer cyrin out loud, there's that IMPALA guy again.

http://photos.yahoo.com/bc/ss3964spd?d&.flabel=fld1&.src=ph
 
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