The most common cause of rough idle quality in engines equipped with this carburetor is an unevenly adjusted idle mixture circuit caused by incorrectly adjusted mixture screws. If a repair manual with adjustment specifications is available, begin with the applicable spec. Quadrajet Adjustments. Quadrajet Idle tube replacement Re: Adjusting Rochester Quadrajet secondary--Update--I took the boat out this afternoon. Transition into the secondaries was smooth for the most part except if I pinned it from 2800rpm it would give that … It will take some experimentation to determine These systems at times overlap in … QuadraJet carbs have three basic tuning variables, and these get people all confused: Primary Metering Jet, Primary Metering Rod, and Secondary Metering Rod. This type does not use a secondary lockout as shown above.To adjust the type of Quadrajet secondary illustrated in the photo.Open the throttle until the rod touches the lever at A.Measure the gap between the rod and lever at B.Adjust … The primary barrels of the carburettor are tiny compared to most four-barrel designs, but this is what gives the Quadrajet its gas milage edge. AIRDOOR TENSION ADJUSTMENTS – (QUADRAJET) If you encounter a bog or hesitation when the secondaries open, more than likely the secondary air doors need to be adjusted. This info may be of use to any of you who have a Rochester Quadrajet 4-BBL carburetor and would like to learn more about it - and specifically, how to tune it for optimum performance: Rochester's Quadrajet carburettors were a staple of General Motors V-8 powered vehicles from the late 1960s until the switch to electronic fuel injection was finished in the late 1980s. The idle screws on a Rochester Quadrajet carburetor fine tune the air-fuel ratio going into the engine during idle. Marine carb spec. Attempting to cure problems by tuning the wrong variable results in lots of frustrations for tuners and car owners. 4MC 4MV Instructions & Measurements M4MC (75 later) Instructions & Measurements. Adjusting secondary air-valve spring tension on a Quadrajet using a small screwdriver and inverted Allen wrench is no piece ot cake, especially in tight engine compartments. E4MC AND E4ME Instructions and measurements. QuadraJet carbs have three basic tuning variables, and these get people all confused: Primary Metering Jet, Primary Metering Rod, and Secondary Metering Rod. Attempting to cure problems by tuning the wrong variable results in lots of frustrations for tuners and car owners. Rochester Quadrajet secondary rod hangers allow you to tune your carburetors secondary metering by adjusting secondary rod height, altering secondary rod power tip … Attempting to cure problems by tuning the wrong variable results in lots of frustrations for tuners and car owners. Quadrajet M4ME Exploded View Secondary metering rod info . Fine tuning on your bracket car between rounds is even more of a drag. These hangers are coded A, B, C, etc., in 0.005" changes in height, with "A" being the highest and "Z" being the lowest. Secondary air valve adjustment is critical to Quadrajet performance because correct secondary air/fuel metering requires a constant depression or vacuum in the secondary venturis. With age the Quadrajet earned a following of technicans who understood its design and recognized its potential. Use a 3/32 allen wrench to loosen the lockdown screw and use the adjustment screw to loosen or tighten as necessary. 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