Young one, back in the day.... *ripples of time*
Before fuel injection, Automobiles used a device called a carburetor to mix fuel into the inlet air stream. Intake manifolds were wet -- meaning there was always fuel in them. In order to enhance vaporization at the carburetor and prevent fuel from condensing out of the air stream onto the sides of the iron manifold, stock intake manifolds were either bolted directly to the exhaust manifold (inline engines) or had a passage running through the center of them for exhaust heat (V engines). The alternative system used passages containing engine coolant coming directly from the cylinder head. Either way, the intake manifold's plenum was always at least 200 degrees F.
So, you see, it is possible to cook food on top of the intake manifold
New York... when civilization falls apart, remember, we were way ahead of you. - David Letterman