Throttle body/butterflies

[Fireopal7]

I have been working on a couple of upper plenums/throttle bodies. I have noticed that when lightly cleaned, it looks like there has been some kind of black material brushed onto the back side of the butterflies which overlaps to the throttle body itself. I can understand why this was done to create an airtight seal forcing the idle air to be provided by the IACC setup. Question is, what is this stuff? Where do you get it? How do you apply it? There must be somebody out there who is familiar with this stuff. Any help/info would be greatly appreciated.

[Ace2cool]

AFAIK, the butterfly valve is just the brass valve. Maybe you're seeing buildup of EGR gases? I'm not entirely sure about this. I do know when I cleaned my TB's, both sides were shiny brass when I was done and it idled far better than before.

[Fireopal7]

I have 2 sets of throttle bodies, 1TT and 1 N/A. When I started to clean the N/A's (off manifold) I washed them down with carb cleaner. With flange side up, the cleaner pooled inside the bores. I let them set for a couple days and they held the cleaner, they were water tight. When I held them up to a light, there were no gaps between butterfly and bore. There was and still is plenty of EGR build up on inside of throttle body and back of butterflies. With TT bodies, I scrubbed them down and removed buildup and painted on "stuff". You can definitely see gaps when you hold them up to a light and aren't watertight. The bores are honed where the butterflies make contact and this black "stuff" was definitely painted on to seal them. I thought it might be a factory fix for imperfect fitting butterflies, but 2 sets of throttle bodies done the same way? When you cleaned your TB's, were they off or on manifold so you could see back side of the butterflies? I can send pictures via Dropbox to show you what I'm talking about. Think I might ask the guy who bores out TB's in Arizona if he has run across this "stuff" since he has seen more TB's than most people ever will. Thanks for reply and I'll try to figure out how to send you pics via Dropbox.

[Ace2cool]

They were on the plenum, but I could see a slight gap, or at least perceived one. But just about every set I've seen has had EGR buildup something fierce.

[Ace2cool]

Just double checked the FSM as well. No mention of anything like that.