What is the purpose of the "heat riser" on 440 HP manifolds?

[Grec]

Just curious as to exactly what it does and how it works.

I'm very close to buying a set to get back to a more factory setup and am wondering what hook-ups, if any, are required to make that riser mechanism work.

Is it controlled by something external or does it work by the engine warming up?

I'm assuming it has something to do with cold engine performance and/or emissions... ?

Thanks.

[Chryco Psycho]

it forces exhaust across under the intake to warm the intake & pervent carb icing , it has a bi -metllic spring that uncoils when warmed
 there is no reason the have this operational unless you often drive the car below freezing

[Grec]

Cool.

Pretty much what I thought.

Thanks!