Carburetor for L-79
Thread Starter
Heel & Toe
Joined: Sep 2012
Posts: 23
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Carburetor for L-79
I have a 1968 corvette with the L-79 motor and a Quadrajet carb, serial # 7029207. I am looking to replace it but don't know what the best match would be. Any help would be appreciated. Thanks in advance.
Drifting
Joined: Mar 2006
Posts: 1,263
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From: Wabasha Mn
Get in touch with Lars on this forum and send it to him for a rebuild.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
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From: At my Bar drinking and wrenching in Lafayette Colorado
The 7029207 '69 L46 (350/350) carb is one of the best Q-Jet carbs ever made. Why do you feel a need to replace it? Nothing will run better than what you have. A real '68 L79 Q-Jet is going to set you back a few thousand bucks and run no better than the '69 L46: the '69 carb is actually a much better carb than the '68.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
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From: At my Bar drinking and wrenching in Lafayette Colorado
The '68 carbs have a very fragile float hinge pin retention design and an inferior float design. The well plug design on the '68 (brass plugs) is also inferior to the revised '69 design (aluminum plugs with o-rings), and those '68 plugs are where the Q-Jet gets its "leaky well plugs" reputation from. You can certainly set up a '68 carb to run well, but the '69 carb is a better, more robust design and is generally more reliable (and you can pick up good '69 L46 cores for about $200, as opposed to the '68 L79 cores which are selling for about $1000).
Lars
Lars
Last edited by lars; May 7, 2023 at 10:36 PM.
Thread Starter
Heel & Toe
Joined: Sep 2012
Posts: 23
Likes: 0
The '68 carbs have a very fragile float hinge pin retention design and an inferior float design. The well plug design on the '68 (brass plugs) is also inferior to the revised '69 design (aluminum plugs with o-rings), and those '68 plugs are where the Q-Jet gets its "leaky well plugs" reputation from. You can certainly set up a '68 carb to run well, but the '69 carb is a better, more robust design and is generally more reliable (and you can pick up good '69 L46 cores for about $200, as opposed to the '68 L79 cores which are selling for about $1000).
Lars
Lars
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Just install a non-window seat in the carb and make sure your fuel pump does not have a faulty checkvalve and is allowing fuel to drain back and siphon the carb.
Race Director
Joined: May 2006
Posts: 18,740
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Lars; I had my carb rebuilt 3 years ago and put on maybe 1500 miles. When my car sits for several days and I go to start it, I have to pump the crap out of the gas peddle before it fires. So what I was thinking is that I would get a new one and keep the original if I ever go to sell the car. That is why I was asking about a good replacement.
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Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
Lars; I had my carb rebuilt 3 years ago and put on maybe 1500 miles. When my car sits for several days and I go to start it, I have to pump the crap out of the gas peddle before it fires. So what I was thinking is that I would get a new one and keep the original if I ever go to sell the car. That is why I was asking about a good replacement.
Have the current carb sorted correctly and replace the fuel pump.......like Lars said, use the non-window seat...this will not allow the fuel level in the bowl to drain back......
The Holley spread bore is not a bad choice but at $700 now....
Jebby
Race Director
Joined: May 2006
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The only good replacement is the spread bore Holley 4775 style carb.......this is a direct bolt on but does not meter fuel as well as the original Q-Jet does. No one else makes a spread bore carb to replace the Q-Jet without using an adapter.....and I strongly urge you NOT to use an adapter......no matter what carb you choose....it will never run correctly with a square bore to spread bore adapter.
Have the current carb sorted correctly and replace the fuel pump.......like Lars said, use the non-window seat...this will not allow the fuel level in the bowl to drain back......
The Holley spread bore is not a bad choice but at $700 now....
Jebby
Have the current carb sorted correctly and replace the fuel pump.......like Lars said, use the non-window seat...this will not allow the fuel level in the bowl to drain back......
The Holley spread bore is not a bad choice but at $700 now....
Jebby