Adjusting the choke

Asked by Sep 26, 2013 at 07:11 PM about the 1972 Pontiac Grand Prix

Question type: General

I probably need to do a choke adjustment on my 72 Pontiac Grand Prix. The engine on
my car is the 400 Cubic inch V 8. I was told the choke position has to be checked
before the car is started. Any advice anyone could give me on this procedure would be
greatly appreciated. Thank You.


Peter

1 Answer

415

I'm going to assume that with the 400 engine you have a Rochester Quadra-jet mounted to the intake manifold. The choke assembly could be controlled by an electric coil enclosure mounted to the side of the carb that heats up when the ignition is turned to *on* that backs off the spring tension that applies the choke plate. The choke coil can be adjusted to the needed application by backing off three self tapping screws an then rotating the outer phenolic cover to get the necessary spring tension inside the choke assembly. The older carbs that did not use the electric choke take-off relied on a coil that was wrapped around the primary throttle shaft to apply the choke plate after the drivers *kicks* the gas pedal when the engine is cold to apply the choke. When the engine is hot the coil relaxes to not apply the choke. The vacuum diaphragm mounted to the carb will partially pull off the choke after the engine starts to allow the engine to run smoothly while still cold, one adjusts the tension on the coil by turning the middle set screw to alter the spring tension. One can also fine tune (adjust) the length of the adjustment arm to get the correct amount of choke pull-off by the vacuum diaphragm. To much pull-off will not allow enough choke and the engine will stall when cold, too little and the engine will flood (run rich). Hope this helps. http://www.carbkitsource.com/carbs/numbers/Rochester/7028219.html

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