How Do I adjust the... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ray_mcavoy · 06-05-2010, 06:29 PM

Q-Jet carbs have a mechanical linkage connecting the primary (front) throttle blades to the rear (secondary) throttle blades. But there is a lockout mechanism that keeps the secondaries from opening if the choke isn't fully open. So make sure your choke mechanism is hooked up correctly and fully opening.

Q-Jet carbs also have secondary air doors above the secondary throttle blades. The air doors are spring loaded and only open based on engine airflow demand. So it's perfectly normal for the secondary air doors (at the top/rear of the carb) to stay closed or only open a tiny bit if you simply rev the engine with the trans in park/neutral.

Is the backfiring something new since the carb rebuild? Or was it doing that before too?

06-05-2010, 06:29 PM	#9
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,404	Re: How Do I adjust the... Q-Jet carbs have a mechanical linkage connecting the primary (front) throttle blades to the rear (secondary) throttle blades. But there is a lockout mechanism that keeps the secondaries from opening if the choke isn't fully open. So make sure your choke mechanism is hooked up correctly and fully opening. Q-Jet carbs also have secondary air doors above the secondary throttle blades. The air doors are spring loaded and only open based on engine airflow demand. So it's perfectly normal for the secondary air doors (at the top/rear of the carb) to stay closed or only open a tiny bit if you simply rev the engine with the trans in park/neutral. Is the backfiring something new since the carb rebuild? Or was it doing that before too?



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