And I suppose my '66 273 manifolds wouldn't have them, right?
When we're talking manifolds, this exhaust throttle, does it serve any purpose? Mine is seized in the fully open position, so I guess it's pretty useless anyhow, but I'm thinking I should rip it out. I saw someone who did that here on FABO.
Hi Anders,
That is a heat riser flap to help with cold starting issues, and carburetor ice. When the engine is cold, the flap stays somewhat closed, and the exhaust is routed up and through a crossover port thats cast into the intake manifold below the carburetor and intake runners to help warm the incoming air/fuel charge. As the engine warms up a bimetal spring slowly opens the heat riser flap allowing the exhaust to flow out that manifold, as its not needed to warm the intake manifold anymore.
My aluminum heads do not have heat riser ports that go to the intake, so i am removing mine off my passenger side manifold, and tapping, and plugging with pipe plugs.
Without it, you just have a bit of a longer warm up time in colder weather, though i doubt you will be driving it in the winter anyways.
Matt