Exhaust/Smog Part?

[Tio Pancho]

Morning All. Don’t remember taking this part off during disassembly, but it appears to go on the passenger side exhaust between the manifold and the pipe. Is this a smog part? Can’t find it in any diagrams I have found. Looks like someone plugged a few holes. It’s in a 77 Chief that will be sniffed in California. Thanks. Have a great day.

Frank

[letank]

the heater stove flapper, most of us remove the flapper and plug the side holes, it is for faster warm up and better running in extremely cold weather... I have gutted mine(s), it passes smog... Runs fine in 25F... the many times I parked in such cold temp.

Yes between the manifold and Y pipe, there is a thin metal gasket with an embossing or crushable ridge

[Tio Pancho]

Thanks letank. Good to know. Not many freezing days in Southern California.

[Stuka]

The annoying issue they cause is when they get rusted, they wont open until there is a lot of backpressure on them. Mine would almost stall the engine, and then once it popped open, the engine would surge.

It is not needed for emissions though, just helps the engine warm up faster as letank mentioned above.

[tgreese]

Splitting hairs, it actually is an emissions component. Heating the manifold shortens the warm-up period for the engine, and that means less time when the engine is sending lots of HCs out the tailpipe. It also improves drivability, since it keeps gasoline from condensing on the ice-cold intake manifold. Kind of like the hot air intake for the air cleaner. I'd guess it's a carburetor-only device, since modern MPI shoots the gas right at the intake valve, and air temperature should not mater except to affect the AFR. Maybe helps TBI, don't know. Possible.

[Tio Pancho]

Thanks for all the info guys. Knowing all this I don't think it will be an issue.
Gotta keep this project moving!