f.e. valley pan?

[randyo]

I know this is a really old post but it comes up and should be factually accurate..

The "heat riser" and "hot air snorkel" off the air cleaner are 2 different things and only the heat riser (diverts hot exhaust gas through manifold)..

If you have ever seen the little flapper valve on a manifold, it is thermally operated and is closed cold to help push heat into the intake.. has been around forever and is for driveability more than emissions.. They "coke" up terribly and on small block GM's, will completely plug..

The hot air snorkel does a very similar action by grabbing hot air from "around" the manifold.. If it put enough heat into the intake to "coke" the bottom side, it would fry the carb first..

Am a 35 year veteran mechanic and hate seeing guys go hunting the wrong thing