69 GT500 choke issue

[jimhyc]

Having an issue with the choke on my car. It's the original Holley with an automatic choke.  It's set on the first notch on the rich side. With that it starts good, fast idle the way it should be. After about 20 minutes running and driving 6 miles the choke isn't fully open. It's still about 10' closed but with no tension on it. I can easily move the blade but it goes back to being slightly closed. If I set it to open fully it doesn't close completely when cold. The car is missing the choke tube to the exhaust manifold. Does it need that additional heat to work properly?
I'm still sorting out little issues after buying the car last week.

[Bob Gaines]

Having an issue with the choke on my car. It's the original Holley with an automatic choke.  It's set on the first notch on the rich side. With that it starts good, fast idle the way it should be. After about 20 minutes running and driving 6 miles the choke isn't fully open. It's still about 10' closed but with no tension on it. I can easily move the blade but it goes back to being slightly closed. If I set it to open fully it doesn't close completely when cold. The car is missing the choke tube to the exhaust manifold. Does it need that additional heat to work properly?
I'm still sorting out little issues after buying the car last week.

Yes if the choke tube is not attached from the choke furnace made into the exhaust manifold it typically does not operate properly. That is why it was designed to have one.

[jimhyc]

Thanks..

[Drew Pojedinec]

Either add heater choke tube or clock it open and deal with the grumpy cold starts.

[FL SAAC]

Try the good folks at dead nuts on

Either add heater choke tube or clock it open and deal with the grumpy cold starts.

[Drew Pojedinec]

Try the good folks at dead nuts on

Either add heater choke tube or clock it open and deal with the grumpy cold starts.

They have some nice gear!
Asset to the community

[Coralsnake]

Installing choke tubes is probably the right idea, but its not always as easy as it looks. Often times old tubes are rusted or broken inside the manifold. Difficulty level can increase quite quickly

[jimhyc]

The stub end of both tubes are in the manifold.  Can't imagine trying to drill those out in that confined space. I do want to install the tubes but not sure if I can clean out the manifold while it's in the car.

[Bob Gaines]

Often times the choke furnace that the tubes plug into are clogged. There is a cavity made inside the exhaust manifold about the size of a roll of dimes. The inside is filled with a stainless steel fiber mesh which acts a filter for the air going the the choke. The air is sucked into the bottom hole of the exhaust manifold choke furnace from the long uninsulated metal tube and connected to the carb air horn by a short rubber hose of the carb. That air is heated by the choke furnace of the exhaust manifold and rises up through the insulated tube to the automatic choke. The tubes many times rust and break off which means the holes need to be drilled out. The inside stainless filter mesh often gets clogged with debris. If you are able to attach the fresh air tube (uninsulated long tube and blow through it then it should work. If it is hard to blow through even a little it need to be cleaned out. NPD and Mansfield Mustang sells a choke furnace rebuild kit. It is next to impossible on the car to drill out broken off tubes. The same difficulty on a rebuild/clean out of the choke furnace. With all this said unless you are taking the engine out for a rebuild etc. getting the right side exhaust manifold off is very problematic. Considering what has to be done cranking the automatic choke to all the way open position like Drew said and dealing with grumpy cold starts can make the most sense to many. 

[jimhyc]

The GT500 is a survivor and don't want to tear it down for a choke tube.  I think I'll suffer with it being a little grumpy starting up in the morning.  I'm the same way waking up at times. 

[Shelbypat]

Be aware, if you are planning to install new chokes tubes. There are 2 models depending of your build date.
Others may confirm.

Patrick