carb choke question
Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
Likes: 32
From: Fern Creek Kentucky
carb choke question
I have been spoiled by fuel injection by various cars since the mid '80's. Not having played with a carburator in years has left me ignorant. My carb is a quadrajet on a '76 L-48. When the engine is cold, the choke plate should be closed right? My choke does not open even when hot.
Instructor
Joined: Nov 2002
Posts: 175
Likes: 0
From: GRIMSBY N.E.LINCS. U.K.
I have been spoiled by fuel injection by various cars since the mid '80's. Not having played with a carburator in years has left me ignorant. My carb is a quadrajet on a '76 L-48. When the engine is cold, the choke plate should be closed right? My choke does not open even when hot.
Tech Contributor
Joined: Aug 1999
Posts: 14,371
Likes: 6,365
From: At my Bar drinking and wrenching in Lafayette Colorado
The hot air choke system on your 76 Q-Jet is a good system if all parts are installed, intact, and in working order. If the choke is not opening and staying closed, chances are that some system components are missing or defective. Visually inspect it and make sure that you have 2 tubes sticking out of your intake manifold on the passenger side: One tube goes to the rear of the carb towards the top, and the other tube goes into the front of the choke housing. Blow into the rear tube and make sure air blows out the front tube where it attaches to the choke. If this is working, do a precise choke setup and adjustment. You can get the step-by-step choke setup procedure from me by dropping me an e-mail request for the Choke Paper:
V8FastCars@msn.com
If your system is missing parts, you can either buy reproduction components for the hot air system, or you can convert your choke to an electric 1980-81 choke system.
Lars
V8FastCars@msn.com
If your system is missing parts, you can either buy reproduction components for the hot air system, or you can convert your choke to an electric 1980-81 choke system.
Lars
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Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
Likes: 32
From: Fern Creek Kentucky
Lars, Although my vette is a '76, I'm not totally convinced that the engine and it's componets are 1976. This car has had multiple owners over the years and it has resided in California, Arizona and now Kentucky. I do know that some parts of the car came off of a '78 vette. I need to look at the vin codes and see if the engine is 76, 78 or otherwise. I have looked but the engine is grimey and I'm not exactly sure where to look. Also the id plate is missing off of the carb and I won't be suprised if other parts are missing as well. Do you have a good reference of what the carb should look like? I will follow your advice and get back with you when I figure more out.
Tech Contributor
Joined: Aug 1999
Posts: 14,371
Likes: 6,365
From: At my Bar drinking and wrenching in Lafayette Colorado
Q-Jets don't have removable ID plates - the number is stamped right into the carb float bowl above the secondary throttle shaft on the driver's side. Number is stamped vertically, and starts with "70XXXXX" or "170XXXXX."
The hot air integral choke carb system was used on all Vettes from 1975 through 1979. 1980 and '81 used the same carb, but with an electric choke in it. This electric choke can be installed into the 75-79 carbs. The only carbs that are different are the 1967-1974 Q-Jets, which use a divorced choke system where the choke coil is not part of the carb.
Lars
The hot air integral choke carb system was used on all Vettes from 1975 through 1979. 1980 and '81 used the same carb, but with an electric choke in it. This electric choke can be installed into the 75-79 carbs. The only carbs that are different are the 1967-1974 Q-Jets, which use a divorced choke system where the choke coil is not part of the carb.
Lars
Race Director
Joined: Nov 1999
Posts: 10,643
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From: Foxfield CO 1970 Convertible
An electric choke can be used with aftermarket intake manifolds that may not have provisions for a heat coil, etc. This allows you to have a functioning choke. Also, the electrics are more reliable (IMO), however, they are not stock if you are doing a correct reproduction.
Tech Contributor
Joined: Aug 1999
Posts: 14,371
Likes: 6,365
From: At my Bar drinking and wrenching in Lafayette Colorado
Most aftermarket intake manifolds do not have provisions for the hot air heat exchanger in the manifold crossover, so an electric choke can be an advantage if using an aftermarket intake. Electric choke is also needed if you use a crossover blockoff type intake gasket. Lastly, if you have missing or damaged hot air choke components and cannot locate replacements, the electric offers a way to get the choke working again. But if you have a fully intact hot air system, use it. It works very well.