I tried searchin but couldnt find any info...

Ive been trying to polish my plenum off my 92 GTA... Only problem is no matter how much I sand I cant get rid of the little black casting pits... were talking hours with an electric, dremel and by hand...

Ive heard that maybe this might be a vette one from the last production that is a different aluminum but i could be wrong... ive polished my runners and valve covers no problem but the plenum wont go... any advice??? should i just paint it?

:hail: :hail:

 

cheap castings and aluminum with a high magnesium content won't ever polish up perfectly. It's only going to get so good.

 

Try this, it should help ALOT.
I'm polishing a plenum right now. I was running into some problems along the way. This site helped me.
It takes a while but the results are well worth it. I might even anodize the one I'm polishing!

http://www.gmtips.com/3rd-degree/dox...m/pol-plen.htm

 

yeah ive been to that site.. have it bookmarked

i will try the 180 method.. ive worked it for hours... i think i just got a rotten plenum cause the runners are so easy to do though..

it was looking good till i got to the 400 wet stage.. then all the pits started showing up?? and polishing it made it look horrible

painted grey plenum and polished runners should look alright

 

I started mine with 60 grit to get the pits out. It took me a long, long time. I did the entire plenum and runners by hand. No power tools were needed.

 

man thats the look im wanting

i took a better look at that site

http://www.gmtips.com/3rd-degree/dox.../plenum/16.jpg

if you look close its kinda rough.. thats what mine pretty much looks like... its awful up close but far away you cant tell...

im just wondering if this is the norm???

ive got like 30 hours of sanding.. is doing it by hand better? i always used the machines..

 

I have a few pits in the corners and areas where it was impossible to get my fingers into, but for the most part I dont have any pits in the plenum. I did it by hand because I didnt have access to machines.

I like doing it by hand though because you can control how much material is coming off and where.

 

ill try again tonight for a couple hours.. i dont think its gonna work... the more i go the more pits i come up on... its like swiss cheese... i got more shine on my runners in 5 mins than i have after hours on my plenum...

guess ill have to snag one off ebay and try another one...

 

Unfortunately you are sanding "cast" aluminum. Really wasn't designed to be polished. The annoying pits are going to be there. If you keep at it you can actually make them worse by "dragging" them.

You have to do as well as you can. Be sure NOT to use aluminum polish and make sure your last step is white rouge not jewelers rouge.

This will make sure the pits and pores you do have don't fill up with black material.

~~~~~~~~~~~~~~~~~~~~
Red 86 T/A 5.0 TPI (LB9/WS6)
~HyperTech Cap/Coil/Rotor/AFPR
~Derale Adjustable Fan Switch ~ 170° Stat
~Flow Matched Injectors ~ K & N Air Filter
~Ported Plenum ~ Pirelli 245/50/16
~SLP TB Airfoil ~ All Else Stock

 

thanks mike.. thats probably what happened.. i went too much with the high speed tools and opened them up a bit... i guess one more weekend wont kill me

i have all the polish and everything.. ill stick to the white... thanks!

 

ya listen to Mike he is the best when it comes to polishing. he has taught me everything I know. Thanks again to mike:hail: :hail: :hail:

 

Ugh.

Mike, I know your method works well.

But damnit, aluminum polish works too. Look at my picture. That was done without any of the expensive *** jewelers stuff. Just Eagle One MAG aluminum polish. I know all the reasoning for not using it as well. I have done my homework.

The jewelers stuff might make a brighter finish, but it can be done either way.

 

Are you sure that wasn't photoshopped?
Looks awesome. I was sanding mine by hand, 20 or so hours in 3 days, and it looked nothing like yours.

This is the best pic I have of mine, it's shiny but not like a mirror,

 

Nah, I dont think its photoshopped

Its all in the final step, just doing it over and over.

 

You are right Adam. The most important thing IS whatever works for you is cool....... and your plenum obviously looks extremely nice and my respect goes to you especially due to you doing it all by hand........ you have paid your dues.

My reference is primarily due to the gazillions of emails I get as to "why isn't mine mirror like" or "why do I have a glaze or cloud like finish"........ etc.

After much trial and error ....... mostly error I came upon the causes of many of these problems. One of which was the use of aluminum polish especially on plenums. For those that aren't "up to speed" on this..... the plenum is rough cast and it has pores.

Aluminum polish leaves black residue and oxidations which fill up these pores and can produce a black clouding. Not only this but you can't get a #12 mirror finish without swirl using aluminum polish. The reason is the same reason it worked in polishing your plenum. It has abrasives. That's cool right up until you get to the last phase you want to acquire which is mirror like.

Some people substitute jewelry rouge for white rouge which fills up the pores with red stuff instead of black. One of the main purposes of ending the process with white rouge is to fill the pores with white material which is less noticeable.

When I did these experimentations I had almost every aluminum polish made, some quite expensive. I was looking for the perfect way to end a polish job. It was very visible that after the white rouge process, applying the alum. polish as a final step "re-swirled" the finish and dulled the mirror likeness.

So yes...... technically it will work and most importantly are you happy? You should be because it looks great.

But I also think you went to many extra hours that most people don't go to achieve smoothness in the metal. That is your true secret........ the extra labor you invested in the metal work.... not the aluminum polish.

How you get there is nowhere near as important as the fact that you have arrived..... know what I mean?

 

Totally. I worked on the initial sanding for about a week, 3-4 hours a day, all on the 60 grit to make sure it was ready for the next grits.

There was a lot of aluminum dust in my garage

I think when I sell the TPI for a better breathing system, I'll try your method and see how it works out

 

Not to change the subject but i was wondering... What kind of system are you running adam? MAFS or speed density?? The reason is because i have MAFS and i want an air filter like the one you have.

 

Its a speed density. If you look on the back left of the plenum you can see the MAP sensor.

The air filter setup I have is crap. It sucks in craploads of hot air from the radiator. I am going to get a more functional ram air filter setup eventually, I just havent had the money.

I'll probably pick up the box from suncoast creations and fab it up to work.

 

Wow Adam, that is one SHINEY plenum :hail:

 

Yeah i was kinda wondering if the airflow was any good right there without ram air, guess that solves my problem. Guess i'll stick to the k+N

 

man you guys are awesome... i worked on it again tonight.. just a single corner... it takes alot of time to get those freaking things worked out...

i used an orbital and 120 grit.. it cut good and eventually i got them all down and its pretty smooth now... finish the rest over the week... the key thing i noticed is change your paper often so it cuts better...

then ill try the steps laid out for polishing with the wheels and bars of stuff man its late

:hail: :lala: