I am replacing the egr valve on the Trans AM. While I have the plenum off I would like to polish the top of it. I have read where sand paper of various grades will work on the rough castings such as on the runners, but what should I use on the plenum that is already smooth and just needs to be shined up?

Any suggestions would be helpful. Thanks.

Bill

 

Your runners are way smoother than your plenum.

For the plenum, start with 180, then got to 220, then 320 wet, then 400 wet, then polish with buffing compounds.

And with the runners, you can start at 320 wet, then 400 wet, then buff.

Under no circumstances should you go over 400 grit. Some people have gone up to a bazillion grit and received awesome results, but more have received better results by stopping at 400 then buffing.

There are tons of threads with plenty of info. Do a search for my username, in this board, for this subject and you will find all of the info you need.