C2 Choke Tube Manifold Question

[Eugene B.]

Members,
I have a question regarding the choke tube, hot air manifold system on my '65 250HP.

The heat tube goes from the choke housing to the exhaust manifold. OK
The fresh air tube goes from the rubber hose connected to the carburator to the bottom of the exhaust manifold. OK

Question is: Is there a third tube inside the exhaust manifold that makes the connection between the clean air tube and the hot air tube? Or does the clean air tube insert into a long hot air tube that goes all the way through the manifold from the top? To ask the question more directly: Are there two tubes or three?

Thanks for your help.

Regards,
Gene

[Duke W.]

Re: C2 Choke Tube Manifold Question

There is a third tube pressed into the manifold, and it can corrode through and quickly foul the choke mechanism with exhaust gas.

Duke

[Jack H.]

Add-on

Duke's RIGHT ON! Reproductions of the exhaust mani internal tube are off-the-shelf at places like Paragon and are a WISE idea to contemplate. IF the internal tube is corroded or rusted through, you're literally playing with fire....

Get red-hot exhaust gas inside the fresh air system and you test the integrity of the seals on your carb's choke. While rare, there have been more than one instance of a Corvette going up in flames from a defective fresh air system!

Getting the original internal pipe out of the manifold can be tricky. It's press fit into a step-bored hole in the mani's upper surface and metal migration over the years can make it a stubborn item to free up and remove. You might have to pull the exhaust manifold and let your local machine shop do the removal/replacement job for you....

[John H.]

Re: Add-on

The tube is pressed in from the bottom and "staked" in place; if it's perforated, replace it.

[Eugene B.]

Re: Add-on

Gents,
Thank you for your replies. The manifold is off the car. In fact, it is a manifold that I recently purchased for the '65. The pipe that is inside the manifold is burned through and both the heat and clean air pipes are broken off flush with the surfaces.

Sounds like it is going to be a bear to drill out the broken pipes and get the manifold back in shape. Any thoughts on what size the holes should be drilled/reamed to and how to go about getting the step at the top?

Also, if I decide to pass on this project, is there a specialist that either of you would recommend to do the job.

Thanks,
Gene