Exhaust port on 215 v8 with 4GC

[GL03]

Does anyone know where this exhaust port goes to on engine with Rochester 4GC? The 2GC has a connection. The service manual does not have this information. I can see on the 2GC the tube secures on the valve cover leading up to the top.

There is vacuum here at exhaust port, and changes idle plugging it. The choke tube is opposite end of this, that works.

here is a pic that has the tube, but I can't see where it goes on Rochester 4GC.

 

[Bob]

That is hot air for your choke but I don't see where a 4GC is offered on the 215. What year and model are you working with?

 

[GL03]

I have 63 skylark with factory 215V8 11:1 compression package which included the Rochester 4 GC. Are you saying that it sucks air in the rear and it is passaged to the front where the choke tube is routed up? When the engine is idling, putting your finger in the rear where the red arrow has a strong vacuum to where it changes the idle significantly and the engine is warm no choke.

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I'm going to investigate this and see if I have a leak in the choke piston.

This is the same explanation in 61-67 workshop manual.​

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[Bob]

OK, that says it should connect to filtered air, so the port it sucks from should be at the top of the carburetor just below the air filter. It could even attach to a port on the air filter itself.

Maybe like this one:

 

[GL03]

Bingo! Bob you solved the puzzle.

There was a statement of filtration, so my carb must've been build from earlier than 62production, sold as 63. They must've seen issues in 60-61 of this that didn't make it into production change till late 62 or early 63. since it doesn't have the tube as you see here. Now, I might just drill the air horn to update this carb, except just browsing there seems to be more of my application without the clean air tube. # 7020034

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[Bob]

Many cars are running without the "clean air feature", and for the number of miles these old cars get, I don't think it will ever matter. But if you like it and it feels good...

 

[GL03]

The clean air tube prevents dirt from going into the choke. There is maintenance needed on the choke, but less required if air is filtered, preventing poor choke performance. I do recall at time of rebuild some dirt inside choke. Another idea might be making a filter or installing one like they have on air suspension at the rear exhaust.