I pulled the IM out of the dishwasher last night, and I'm planning on taking it to a local shop for bead blasting as a final cleaning step. Should I wait until the switchover butterflies are out? Is glass bead OK, or is plastic necessary? Should I do this at all.

Yes, plastic is necessary

That said he could do it with glass blasting. He deals with Nuclear Reactor Components and has an adjustable system (much comparable to your grinder... infinite speed/velocity adjustment) that he said he could remove the corrosion without removing any aluminum. Will do it for $40-$45.

Knowing what I know about nuc reactors (I got a general idea of what goes on being that I work with them on subs) not the slightest bit of material can be removed from them because the tolerances are so tight... so I have some faith in him. That doesn't mean everyone will know what they're doing... but this guy seems to. And I'll make sure to state that if he destroys it, he'll be buying me a new one. Simple as that :)

while plastic is harmless to the internals of an engine silica is abrasive as hell. And there will be tons of silica media left embedded in the IM walls after he's done in the form of "silt" and with a micron size comparable to talc. Ultrasonic cleaning would be even better due to the vibratory waves helping dis-lodge the particles. But finding a tank that size could be difficult and spendy.

I'm not going to have him TOUCH the inside though. I already have that spotless thanks to the bulldozer and the 4+ bottles of carb cleaner. I'll make sure the tell him to not touch the inside as well. Think if I tape it off that would be a good deterant? He doesn't work with the regular booth either. Since he deals with reactor components, which are usually quite large, he has rooms that he does this in. I'll get a better feel about what's going on when I talk to him next week.

Thanks for the heads up Mance... much appreciated.

If it's already *pretty* clean, what do you need the Bead Blasting for? You're just going to be grinding a lot of what's left anyway, so I'm not sure that having him bead blast it anymore is worth it. I think the main reason for this initial cleaning was to make sure our grinding material didn't get all gummed up with dirt and oil which would really shorten its useful life.

Cuz it was a NH car, I'm guessing it was subjected to a LOT of salt... and has developed a nasty crud all over it...

I just wanna remove the crud. Purely cosmetic in the long run, but something I want to have done. The inside doesn't need to be touched... cuz with all the time I spent on it, I got pretty much every drop of sludge out of it... carb cleaner is a beautiful thing plain and simple.

Less confused now?

I don't have any idea how clean it needs to be for the powder-coating to adhere...

any left over material on the surface would probably make the powder coating fall off/peel... ya know?

powder-coating is a relatively thick coating which would prevent the IM from shedding it's internal heat and running warmer than no coating. Bad thing for intake temps. Black anodizing is a chemical-electrical process that etches itself .002" into the surface turning the metal black (or any other color but with less heat dissipation) with no insulating layer. Additionally black anodizing will shed the heat faster than raw aluminum or any other color.

I might just leave it alone too cuz I like to stock look under the hood. Brings no attention to any hint of power... not that there's a problem with that currently ;) Down the road... maybe :)