Topic: Rochester Quadrajet
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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Hi All,
|UPDATED|6/6/2018 8:51:47 PM (AZT)|/UPDATED|
I have a question in regards to the carburettor on my 69 427 Big Block Corvette.
I was just wondering with the choke open should the air valve lockout lever tang (circle in red) be in that position? In the current position it prevents the secondary air valves opening.
I have done a little bit of reading of the Rochester Quadrajet manual and it seems to suggest that the tang should drop back if the choke is open allowing the air valves to open freely.
I am by no means knowledgeable on carburettors and just asking for advice.
I have previously had an issue where my throttle wasn't adjusted correctly resulting in the throttle only opening 30% resulting in my secondaries never opening. I have adjusted the throttle now to the correct position so it opens 100% when the pedal is to the floor.
Thanks for any help and advice.
|UPDATED|6/6/2018 8:51:47 PM (AZT)|/UPDATED|
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IIRC, the lockout on mine prevents the secondaries from opening and yes it should release when the choke is fully open.
1973 L-82 4 spd
I am not sure that the choke is fully open by looking at the angle? I am thinking that's why it's not disengaging the lockout?
Does the choke coil/rod look like it has been installed backward?
Could this be why the choke isn't fully opening?
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First thing...the choke is NOT fully open in that pic. Second thing, what you have circled is the AIR VALVE lock-out. The actual secondary throttle blade lock-out lever is down on the bottom. The design is for the secondary throttle blades to open with the throttle linkage(at 3/4-full throttle), and the air valve is controlled by the amount of air rushing past them with the throttle blades open.....like a variable venturi effect. The air valve assy keeps the engine from bogging down completely when the secondary throttle blades go wide open.
So...first thing I would do is adjust the linkage from the choke coil to the choke lever, and get it to be fully open with the engine warm. Then see if full throttle will open the secondary throttle blades. NOT the air valve( on top), but the throttle blades themselves. If the throttle blades are not opening, the air valve will not move either.
Sometimes, the little lock-out "tang" for the secondary throttle blades will gum up, of otherwise stick, and keep the secondaries from opening. You have to make sure the choke is opening fully when warm before doing anything else. 
|UPDATED|6/7/2018 10:32:16 AM (AZT)|/UPDATED|
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A good reference source is the Rochester Quadrajet book put out by HP books.
1973 L-82 4 spd
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|UPDATED|6/7/2018 3:56:20 PM (AZT)|/UPDATED|
1973 L-82 4 spd
Adams' Apple said:
First thing...the choke is NOT fully open in that pic. Second thing, what you have circled is the AIR VALVE lock-out. The actual secondary throttle blade lock-out lever is down on the bottom. The design is for the secondary throttle blades to open with the throttle linkage(at 3/4-full throttle), and the air valve is controlled by the amount of air rushing past them with the throttle blades open.....like a variable venturi effect. The air valve assy keeps the engine from bogging down completely when the secondary throttle blades go wide open.
So...first thing I would do is adjust the linkage from the choke coil to the choke lever, and get it to be fully open with the engine warm. Then see if full throttle will open the secondary throttle blades. NOT the air valve( on top), but the throttle blades themselves. If the throttle blades are not opening, the air valve will not move either.
Sometimes, the little lock-out "tang" for the secondary throttle blades will gum up, of otherwise stick, and keep the secondaries from opening. You have to make sure the choke is opening fully when warm before doing anything else.
Thanks I will start with ensuring the choke opens fully.
With the choke coil, I will reverse this as literature is telling me it is around the wrong way.
Also the choke coil cover is missing, I know this has an impact and may result in the fast idle not kicking down when warm?
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Without the choke cover on, I don't think the engine heat will warm up the coil as fast thereby slowing the opening of the choke.
|UPDATED|6/7/2018 6:10:51 PM (AZT)|/UPDATED|
|UPDATED|6/7/2018 6:10:51 PM (AZT)|/UPDATED|
1973 L-82 4 spd
73shark said: Without the choke cover on, I don't think the engine heat will ever completely warm up the coil and thereby opening the choke fully.
Makes sense, I don't actually have the cover. As long as the choke closes it is fine, I should be able to just manually kick the fast idle down after a couple of mins?
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Vette(s): 1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.
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Yes you can kick it off of fast idle but if the choke is not completely open, it will not unlock the secondaries.
1973 L-82 4 spd
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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