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Old 08-29-2012, 09:57 PM
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my carb is a 75-77 and i have the needles for the pre 75..........

Incorrect Primary Metering Rods
Results in: Poor idle, rich idle, ineffective idle mixture screws, surging at cruise, poor mileage, poor cold-running characteristics, hesitations off idle and/or at cruise, poor manifold vacuum with resultant ancillary problems.
Comments: In addition to seeing incorrectly sized metering rods for the application, I am also seeing carbs with the WRONG rods installed. Pre-75 (up through 74) Q-Jets use metering rods that are approximately 2.47 long overall (total length from the metering tip to the extreme top of the rod). 1975 and newer Q-Jets use rods that are about 2.40 long. The early rods typically also have just a plain number stamped into them (like, 44), or will often have the letter B after the number (like, 44B). The later rods will often have the letter K or M after the number. If an early rod (long rod) is installed in a post-75 carb, the actual shank (body) of the rod will be stuffed down into the jet, resulting in a severe lean condition with associated marginal drivability. Likewise, if a late rod is used in an early carb, there will be virtually no lean-out from the power piston at idle or cruise, and the carb will suffer a severe rich-running condition.
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