humiliategravity

What is the best way to accomplish this? I have a carb/manifold choke compatibility issue so I'm going to try running the carb with no choke. I've heard that I may lose secondaries with a disabled choke... can this be prevented?

Thanks!

Dave

cardo0

Really the best fix is to see if lars will help you here (www.V8FastCars@msn.com). lars rebuilt my Qjet and removed the choke blade but left the linkages needed for the sec air vlv. The choke blade has to come out and the linkage (choke rod) that runs inside the carb body (turns/wiggles out with a careful 90* roll). But the vacuum break assembly needs to stay intact to allow the sec air vlv to open. Also the choke coil assembly can come off and the one associated link - but thats it!
Okay Dave i found yer other post about Qjet chokes on a ZZ4 intake. What yer '73 used was the same as my '74 and its called a divorced choke. Now Edelbrock sells a retrofit plate (that fits on yer intake) for this, part #8901. But it will do you no good. Your ZZ4 (nice motor and I'm jeoulous) don't have the exhaust crossover port in the cyl heads. So no heated crossover under neath the carb to heat a divorced choke. Sorry but this puts you back to removing the choke blade.
Now if lars is to busy - very nice man but probaly has bigger and better things to do - www.customcarbs.com (near me in Ontario, CA) will sell a nice rebuilt Qjet custom built for your ZZ4 with late model electric choke for $350. But hey, you could give'm a try and see if they'll just remove the choke on yers??
Good luck neihbor. cardo0

lars

Dave -
How to do it depends on the year of your Q-Jet. What year and/or carb number carb do you have?

humiliategravity

Thanks for the responses, guys. I won't be able to get the carb number until tonight, but it's a Rochester 4MV from a 73 if that helps... pretty sure it's the original. It does have a divorced choke that mounts flat against the manifold.

Dave

humiliategravity

I looked at the carb last night and it had numbers all over it... I'm really not sure which one signifies its model number but here's a guess:

7043926

So I should remove the choke blade and linkage, then I'll be good to go?

lars

That's not a good number for a Vette carb, but as long as you're working with a divorced choke system on a pre-'74 I know what you have.
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No, you don't need to remove the blade, and removal of the blade will not ensure that the secondary lockout does not engage. I'll post up some instructions for you this evening once I get home.

humiliategravity

Thank you. That would be great!

lars

To “lock open” a Q-Jet choke, the following instructions should be followed:

First, note that the choke pulloff and the secondary airvalve control are one and the same unit. You cannot remove all choke components and the choke pulloff without adversely affecting secondary operation. The choke pulloff controls secondary opening rate, and eliminating the pulloff will result in a massive bog or stumble when you go into the secondaries.

Secondly, it is imperative that the secondary lockout lever be fully retracted if the choke is locked open. Depending on how you lock the choke open, the lockout lever may or may not be retracted. By locking the choke per these instructions, the lever will be fully retracted and your secondaries will operate.

There are 2 different styles of Q-Jets, and the method of locking the choke in the open position differs between the two.

1967 – 1974:
This series carb uses a “divorced choke” system. There is a bi-metallic spring mounted in a box on the intake manifold heat crossover, and there is a steel rod connecting this spring to the choke lever on the carb. To lock the choke open, locate and identify the steel counterweight/fast idle cam lever. This lever is located on the passenger side of the carb, and it rotates on a shaft between the outer steel choke pulloff mounting plate and the carb float bowl. The big end of the lever points forward, and you can lift it up and push it down. It is the biggest moving part in the choke linkage system. If you push it fully down, it will hit and rest against a casting protrusion on the carb. You want to push it down to this position and use a plastic wire tie wrap or a piece of safety wire to secure it solidly against this casting protrusion stop. In this position, the counterweight will fully retract the secondary lockout and the choke will be wide open. Disconnect and remove the choke rod between the spring coil and the carb choke lever.

If you’d like to take the choke disconnect one step farther, you can remove the choke blade, remove the choke intermediate rod, and pull the choke shaft out of the airhorn. You still need to keep the counterweight/fast idle cam secured to the carb casting protrusion. I have done the choke blade removal on several carbs, and I have never noticed any difference in performance/power from a carb with the components in place.

1975 – 1980
This series carb uses an integral choke system, identified by a round, cast aluminum housing with a black plastic cover on the passenger side of the carb. 1975 – 1979 was a “hot air” choke system using two steel tubes connected to the manifold. 1980 used an electric choke with a single electrical connector attached to the cover. On this carb, simply loosen the 3 choke cover attach screws and rotate the cover ½ turn clockwise. Snug the screws back up. This will lock the choke fully open, and will retract the lockout lever. If the cover is attached with rivets, you must drill out the rivets, tap the holes for #10 screws, and install screws after the cover has been rotated. Or, you can re-install rivets if you really like the rivets…

These methods for choke lock-out will assure that the secondary airvalve remains functional, and assures that the lockout lever is fully retracted for correct secondary operation. While you’re doing this operation, test your choke pulloff by attaching a vacuum hose to it and sucking on it: the diaphragm should retract fully and hold a vacuum. If not, replace it to assure correct secondary airvalve operation.

1969c3mandy

thanks lars...you are a god! I needed to know too!

humiliategravity

Thanks for the help, Lars. I'll give it a shot.

Dave

PS - I've really enjoyed your technical articles on carbs & engines, etc. They're easy to read and well grounded in science. Have you considered writing a book?

73 LS-4

I can't recall the company that made them but there was a companny that made an electric choke that bolted to the intake manifold in place of the divorced choke heated spring, so a heated crossover wasn't nescessary. I thought about doing this myself after finding that the 73 LS-4 divorced choke wouldn't quite work with the 68 L-36 intake, I fabricated a new choke rod that made the combination workable though, albeit I have to reset it everytime I want the choke to come on by tapping the rod with my fingure, but it pulls off correctly. I was thinking it was something like carbparts.com or something like that, but they had lots of q-jet parts there.


Pat Kunz

lars

The outfit that sells the electric divorced choke conversions is Carbs Unlimited. They're at:
http://www.carburetion.com/quadrajet.asp

humiliategravity

Thanks for the tip. Unfortunately my issue is compatibility with the intake manifold, and the electric conversion kit they sell uses the same attachment as the divorced choke. I actually called Carbs Unlimited last week about it... nice people there.

I'm curious to see how my Vette runs without a choke, especially in the cold, cold southern California winter If I'm having problems I'll install a manual choke.

lars

We all run no-choke carbs here in Denver with no problem. At worst, you'll get a lean backfire pop out of the carb when cold-starting or when cold-running, and it will be a little balky for the first couple of minutes after start-up. After that, no problem.

joe73vette

Lars, I wonder how that would work when switching to vortec heads and a vortec performer manifold? I drive mine in cold CT weather, so I want the choke/fast idle to work after the conversion. Thanks, Joe