drwet

Weather is nice enough now around here that I got the '79 out of storage. Fired right up and runs great. Problem is after driving it for five or ten minutes, the choke comes back on and I am continually trying to kick down the fast idle. The carb is a 770 Holley Street Avenger with an electric choke. The choke is set up properly. The heating coil works. There is power at the choke when the ignition is on. When I turn the ignition on without the engine running the choke comes off nicely within about three minutes. With the engine running, however, the choke doesn't quite open as fully. I have a couple of ideas. One, does the choke wire on a '79 supply power at all times when the engine is running or does it shut off after the engine warms up (which might allow the choke to come back on)? Second, is it possible to assemble the choke incorrectly so the vacuum pull-off works in reverse and actually applies the choke? Any Holley experts out there who might know?

GUSTO14

Be sure that you have a full 12 volts going to the choke from a switched source and the ground side is going to a good location on the engine.

If you have the full 12 volts, you can also loosen the screws that hold the black plastic cover to the choke assembly and turn the choke cover to pull the choke off earlier. The best way is to warm the engine fully and make the adjustment then with the engine running. Adjust it so that fully warmed, it pulls the choke fully open.

Good luck... GUSTO

waynelap

Make sure the pin on the carb is in the hole on the coil. I missed it on my first install and had a similar issue.

drwet

All that stuff checks out. I had the carb off and bench tested the choke. Works perfectly. Put it back on the car and turned on the ignition. 12 volts at the coil (14 when running). Choke works perfectly until I start the car. Then the choke closes slightly from where it was when the car was off. Enough that the fast idle will come back on periodically. Seems to be a vacuum related problem to me.

waynelap

My choke is set to, when the engine is cold there is about 1/8 in gap between the butterfly and the carb horn. It is never fully closed. When the car is warm the butterfly is fully open and there is "some" tension on the butterfly holding it open. I don't understand why vacuum would have any effect? The only other thing I would check is that its wired correctly and not to a source that is drawing power also when your driving. (eg electric fans) I have the manual from my carb that describes the choke adjustment if you need it but I'm sure the Holley site has it also. Good Luck.

olescarb

The choke piston uses vacuum that flows thru the choke system to open the choke about 1/4 open once the engine starts but that colder air from the engine compartment can cause the choke to not fully open. We have had to restrict the air that flow into the choke to allow the choke to get to fully open in cool weather, we used a cap with a 1/32" hole placed over the clean air inlet to the choke housing which allowed the choke piston to function properly and allow the electric choke to fully open as designed.

I hope this helps Henry @ oles carb

drwet

Yes that does help. That makes a lot of sense. The weather is still cool here. I will give that a try. Thanks.

But it still doesn't explain why the choke opens fully with the engine off, but comes back on slightly when I start the engine. Its almost as if the vacuum pull-off is working in reverse. Is that possible? Could I have installed the linkage backwards last time I rebuilt the carb?