When I took the upper intake manifold off of my 2001 f150 4.6 there is a black box under it from what I researched it's the plenum but I also seen where it's called the lower intake can somebody please help?And what does it do?

 

Technically, it could be called a plenum. An intake manifold is composed of a plenum and runners. So in your case what you're looking at is both the lower intake and the plenum. The upper intake would be the runners. In your case. The plenum is where the throttle body attaches. Sometimes the plenum is on top or on the middle, which can confuse things.

But Ford calls it a lower intake manifold (intake manifold - lower) so if you're searching for parts that's your best bet.

 

Just came across this video and see that Ford ran the passage from the throttle body to the plenum right through the center of the upper manifold down to the lower manifold where the plenum then redistributes the air in to the upper manifold. It's an odd design, there's a gasket between each connection. The air goes down through the center to the plenum, then curls back up in to the runners, then each runner goes up ands curls back down to each intake port. I learned something, never seen such a thing. Lots of changes of direction. Many car makers just put the TB directly on the front of the plenum.

Anyway, sorry if I confused things.

 

I am working on a truck with this plenum and the gasket that came with the kit doesn't fit over the brass nut zerts. Would anyone know what the right gasket is for this?

 

f10066,

What year and engine are you working on? Gasket part number and source?

Jimboy

 

The gasket came with the set with the engine not sure of part # will look at it again today see if I can see a #. It's a 2004 f150 4.6

 

I found the box that gasket kit was in. It's a felpro MS 92614