AudiWorld Tech Articles

Tech Article Title	Author	Date
Polishing 12v Intake Manifold	Greg Kiernan	2005

To start you should first gather all the tools neccessary:
1-2 sheets of 60 Grit Sandpaper (or coarse emery cloth)
1-2 sheets of 220 grit sandpaper (or medium emery cloth)
1 sheet of 320 grit sandpaper
1 sheet of 400 grit sandpaper
1 sheet of 600 grit sandpaper
1 sheet of 800 grit sandpaper
1 sheet of 1000 grit sandpaper
1 sheet of 2000 grit sandpaper
2 IM to Head gaskets
1 Upper to Lower IM gasket
6 New Injector Seals (12 if your going to remove the injectors from both the IM and the Fuel Rail)

Optional Equipment:
A random orbital sander (5" preferable)
15-20 60 grit sanding pads
10-15 220 grit sanding pads
2-3 cans of carburetor cleaner
1 Plastic bristle brush

If you happen to get the extra tool and materials, you'll only need 1 sheet of each grit sandpaper. Ok to begin your IM should be removed from the car , the fuel rail and injectors should be removed, and the upper and lower portions of the IM should be seperated. Follow steps 1-23 here to remove the IM:
http://www.12v.org/maintenance/repairs/checkvalves.php
You'll probably have something like this in front of you:

I opted to clean both halves while i was at this point, that's where the carb cleaner and the brush comes in handy. Once you get your IM all cleaned:

flip it over, sit in something comfortable and prepare yourself for the long haul. Your first goal in this is to remove ALL of the pits left by the sandcasting on the surface where you want to polish. If any pits are left they'll show bright as day in your polish job and you'll need to redo most of the work. To remove them, i used the random orbital sander with 60 grit pads, if you go this route just keep the sander moving so you don't create any dips in the metal. You can also do this with 60 grit sandpaper or coarse emery cloth, this would take a very long time so if you are going to do it this way just be ready to put alot of hours in. Once all of the pits are out your going to want to switch to the 220 grit sandpaper (or sander) and smooth out all of the score lines left by the 60 grit. The way that i do this is, through the majority of a certain grit, i sand straight with the runners, leaving a bunch of horizontal lines. Just before i'm done with that grit, i run the sandpaper perpendicular to the runners to score it. Now when you go to the next more fine grit, continue to sand straight with the runners, until the perpendicular lines are all gone. Once they are gone you can score the surface again and switch to the next grit. It should look something like this now:

After 220 grit, you should now use 320 grit, the rest of this should all be done by hand and wetsanded. If you like the look of brushed aluminum, 320 grit leaves a very nice brushed aluminum look. If you prefer this look over polished then you can jump to the end where you finish the piece. From 320, it goes to 400, then 600, then 800, then 1000, then 2000.
You can skip some of the grits and jump to a higher one, just keep in mind that the more stages there are, the easier on you and your arm it will be. Your piece should now look pretty close to this:

The last thing you should do is clear coat it with an engine enamel. This will keep the IM from oxidizing which can happen very quickly if you live near the ocean or where they salt the roads for winter. My IM is still off the car as i am working on the heads, but once it's all back together i'll post a picture of it in the car. For now this is the best i can do:

If you need any help feel free to email me, or contact me on AIM (anokiernan), or MSN (anokiernan@hotmail.com). Good Luck

Here's a picture of it in the car

And no those are not the plastic valve covers. They were painted with a black engine enamel and the rings were polished with a similar method.