When prepping a surface for a new gasket, at what point is it considered "clean enough"? I'm midway through the plenum fix with my new Hughes plenum plate and I'm getting reading to re-install the intake manifold. I have the surfaces smooth to the touch but they are not 100% shiny, bare metal. There is some dis-coloration that remains. If you close your eyes and run your fingers over the prepped surfaces, you cannot feel any transition. Is this considered clean enough or should I keep cleaning? Also, I'd love to hear any recommendations for best methods for preparing surfaces for new gaskets.

 

I use a whizz wheel on an air grinder....... (they are little abrasive pads, different colors for different metals...... clean things up fantastic, but, require the air tool... and air....) Then I hit 'em with brake, or carb cleaner. Surfaces are squeaky clean, you could eat off of them. (and then clean 'em again before assembly.)

 

Discoloration should be ok, as long as they're smooth like you say. I cleaned mine with a razor blade, then wiped the surface down with mineral spirits. I also could not get all the steel surfaces shiny, but its been about 20k miles since I did the plenum and haven't had problems.

 

I agree with jswain, dicoloration is not a problem. I razor bladed mine then polished with extra fine stone (more than necessary but I had time to kill).

Smooth flat surface is the critical part. From the factory, the casting uusally has mill marks that do not present a problem (I previously worked as an engineer at an aluminum foundry. We did intakes as well as other items).

 

I hit my intake manifold mounting surfaces with a wire brush wheel. made sure to put a aluminum foil tray in the lifter valley to keep crud out , then toss tray and all the crud that fell in it.