| Since I started polishing over the last 2 years I've been hit with at least 50 emails on how to properly do a plenum so here is the break down on everything you need to know. Supplied throughout this explenation will be Eastwoodcompany.com pics to show where to get these easily. This is a bit more detailed on what and how to polish because I see a lot of plenums done very half-assed and from people that don't entirely understand the concept of polishing. Either way her it is. ****TOOLS NEEDED*****
(4) buffs, 3"-5" in diameter La-Z-Link
(1) buff arbor (for the above buffs)
(1) high rpm drill (not cordless)
(1) set of greasless compounds (80, 220 & 320 grit) La-Z-Link
(1) rotating wire wheel La-Z-Link
(1) pair of goggles and (1) breather mask.. (trust me on this.)
(1) pair of clothes that you don't miss (again... trust me)
(1) grinding bit (aluminum oxide preferred)
(1) assortment of sand paper (use only 80, 220, 320 grit to match the compound.. it's important for finish)
(1) white rouge polishing compound La-Z-Link ****Getting started**** Make sure you have a very open area and clear things out of the area that you don't want to get dust on as this process get everything in and around it ... filthy. Keep in mind this a LONG process, normally it takes about 40+ hours of labor to do a plenum correctly, so be patient... THIS ISN'T AN OVER NIGHT THING. The original plenum you have is most likely dirty so taking the time to clean it up now will save you time now. Engine degreaser helps to get a lot of the buildup off to get started. Once you've cleaned it up your going to use rotating wire brush ... attaching it to your drill. Apply only about 2-5lbs of pressure.
* It's important in buffing to let the brushes/buffs do the work for you. Pushing hard only destroys your materials faster.
You'll notice the plenum taking on a cleaner look as you begin to go over the plenum. It's important to get in the cracks and grooves as much as possible. This will help out SO much when you begin the process in a minute. You should have a nice clean plenum with a silver tone but still have a rough cast look to it. Soon we will begin to clear all that off. ****Removing cast marks***** The stock plenum has some mean cast marks running along the front, back and sometimes sides of the plenum. Some polishers just work over them, but to truly have a stunning plenum you must consider removing them. You'll use your Aluminum oxide bit and begin to cut them away to get it as close to the metal as possible. DO NOT LEAN INTO THE METAL AND CUT INSIDE, just enought to take it down to near surface height. Don't worry about mistake as we will be touching those up shortly. Remove all the casting lines you deam necessary. Some examples are here -> Originally - La-Z-Link
After - La-Z-Link You can also remove the plenum pegs if you really want to get crazy. I did this back in the day when I used to offer the service. I think it looks hella trick but I used to utilize a small dremel cutting disk to remove the peg portion. But if this scares you don't worry about it. See example below -> Before - La-Z-Link After - La-Z-Link ****The meat and potatos**** 80 grit is your friend. This is the perfect grit (ie, texture roughness) to begin to remove the cast on the outside of the plenum. First attack the plenum using 80grit sandpaper to get as much of the heavier cast in the open areas as possible. This is just the first stage in a long line of attempts. After you've taken that cast marking down a tad, it's time for the buff. You'll need to put a buff onto the arbor at this point and apply a bit of the greaseless compound onto the buff wheel. You will want to apply the compound at a downward angle. The compound will begin to melt onto the buff. Let the buff sit for a few moments to begin to harden and create a hardened texture. This process will be repeated many times, so get used to. You'll then begin the long process of removing cast and going over the cast mark from removing the lines. This is probably the longest portion of the process an should last about 30+ hours alone. You'll want to continue the process till you begin to see the cast lighten and the metal begin to clear giving way to clear silver tone. Once and only once you've cleared off all the cast you possibly can we begin the real polishing process. But, I can't stress enough the importance of removing as much cast as possible. Now we are going to "texturize", the process of polishing in 2 directions only not just the "all balls out" method from earlier. Swaying back from right to left as your working your way down as far as you can go on that section. Then just rotate the entire piece 90 degrees and do it again in swaying motion. Basically, just do one whole side or section, then do it again but from a different angle. The process will allow a smooth even flow over the plenum for that grit and remove as much heavy scratches in the metal as possible. Because we go to higher grit (the higher the less abraisave or rough) after this those scratches will stay there.. so remove the scratches the first time while your on that grit. *Going back and forth between grits will comletely destroy the look of your piece and you'll have to start all over again* Completed pic of process - La-Z-Link I know it looks good, but you still got a ways to go. Now the next grit. Clean the surface of the plenum with a wet rag to clean the surface. Then using only 220 grit sand papers go to town on it. Sand as much and as well as you can again with the sand paper. Put on the "new" arbor, not old one, and apply the 220 grit greasless compound. Remember to go thuroughly and take your time. You'll repeat the rinse, sand paper and buff with the 320 grits but remember only matching grit #'s in process. ***Polishing** Once all the grits have been used and you've wiped down the plenum it's time to polish. PS- I wipe down the plenum with Windex to really get all the dirt off the surface (old trick). Same process to apply the white rouge compound to the buff. Let it dry for a moment then repeat the swaying process and you'll notice the new luster and also a black film. This comes with buffing wipe it off using a screw driver to clean the running buff from time to time. Put some time into this stage. You should have a nicely finished plenum at this point. You can always flip for chroming if the shops are available in the area. It's usually a pretty penny though, but the differences are great. On left- Polished plenum On right -Chormed plenum
La-Z-Link Good luck and above all else take your time with this and don't rush throught the stages. You are going to get dirtier than you've ever been before so clean up, clear your area and wear protection at all times (I mean the goggles.) Enjoy.
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How to polish your plenum- The basics 101 - 
