General Category > Quadrajet Carb Talk and Tips

Rear air door opening vs CFM

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Frank400:
excuse my ignorance, but where does rochester instructs to measure secondary air door opening ?

Kenth:
They did that in 1965 and 1968 bulletin 9D-5 among others because the 1965-66 Quadrajets had the adjustable stop on the dash lever for air valve opening.

Later units have shafts with a fixed stop for the degree of opening of the air valves depending on the application.

Frank400:
ok I see, wow thanks for the info, never worked on any rochester older than 67 so that is a new one for me.  Cool info.

Cliff Ruggles:
Your are lucky.  The 1965-66 units are HORRIBLE and gave the entire line of carbs a BAD reputation that still exists to this day.

The secondary dampening system is HOPELESS.

The plunger type fuel inlet valves with the bypass port are HOPELESS.  Even the "conversions" that come in the rebuild kits with a push-in or retainer held in fuel inlet seat and bypass plug are horrible.  99 percent of the ones I've had in here leaked at the "O" ring on the bypass plug.

The leak rate for bottom plugs is 100 percent, and 90 percent will be leaking at just about every plug in them including in the very front where the fuel filter housing screws in.

Coincidentally I have an early 1967 Chevy small block Q-jet in here right now that still used the crappy fuel inlet valve set-up.  It is leaking at all four bottom plugs.  The plug just below and to the left of the fuel filter housing is leaking.  The bypass plug driven in during the last rebuild is leaking.  I only took it in for a heli-coil install, but it was fully assembled so now I've inherited a MESS!.....FWIW......

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