Personally, I think it’s a crime when people paint their aluminum engine covers. Polishing them is SO easy and the results look so good. Others may have other and maybe better methods, but here’s how I do it.
We start with a typical 30+ year old clutch cover, clear coat yellowed, tarnished, pitted, and scratched.
* Pull the cover from the engine. I suppose it could be done with it on, but having it in your hands makes it much easier.
* Use some heavy duty paint remover to strip the factory clear coat. I’ve even used the stuff called ‘Aircraft Remover’, the funny thing is that the label says not to use it on aircraft. The suff in the spray can is a waste, buy the gel stuff in a can and brush on. You may need additional passes to get it all off.
* Start hand sanding with 200 grit sand paper (100 if there’s a lot of damage) . Then to the kitchen sink to do the wet sanding (note I’m single and live alone). I generally used one sheet each 300, 400, 600, 1000 grit. The higher the number the finer the grit, the smoother the finish. The smoother you get, the closer you’ll get to that mirror like finish. This part is the most time consuming and requires a lot of elbow grease.
* Now back out to the garage for some serious power polishing. I’ve thought about getting a bench grinder, but currently I use my $15 Harbor Freight Angle Grinder with buffing wheel and some jewelers grade abrasive (green). Spend a couple of extra bucks for the thicker pad, they are pretty cheap any ways. You can also get little buffers for those hard to reach places. When I first started I used a hand drill buffing wheel, but honestly the angle grinder spins a lot faster and has a lot more power. Buff away in all directions on all sides. With some practice you’ll get a feel for the right amount of abrasive and how hard you have to work it. I put my parts a bench vice using an old rag to protect the cover from the metal of the vice to hold it while I’m buffing. Wear eye protection too and take all necessary safety precautions. It’s easy to loose control. I’ve shoot a tappet cover across the garage before. Plus buffing wheel bits and abrasive residue will be f
* Then for the final touch. I user Mother’s Aluminum polish with either an old cotton t-shirt, polishing rag, or an old cloth baby diaper for the final rub down (keep those old cloth baby diapers, they are awesome for polishing). Again, this part takes more elbow grease, but the work is worth it.
* Remount the cover with some nice stainless steel bolts. Done.
A clutch cover takes me about 2 and a half hours, smaller parts less.
In the past I’ve tried putting clear coat over my polishing work, it only dulled the shine. Sure, having that raw aluminum exposed increases it’s chances of it tarnishing again, but I just hand polish with Mother’s Aluminum polish once or twice a season when I’m detailing my bikes.