Advice Request: Refinishing M20 Aluminum Valve Cover?

[zipzam]

Hey Fellas.....

I'm looking for advice from my fellow E30 enthusiasts who have experience in restoration techniques, specifically for refinishing the M20 motor's aluminum parts.

I'm a stickler for originality, so I'd like to restore the aluminum valve cover and the other associated aluminum parts, to as close to the original cast aluminum finish as possible. I realize that this might be impossible, as a brand new valve cover's bright finish is the result of the original aluminum casting and they were never originally painted or anodized plated.

In the past, a simple option was to first bead blast the stained aluminum parts and clear coat them in order to seal the porous aluminum after the blasting process. Unfortunately, after clear coating the bead blasted aluminum surface, the finish turns a drab grayish color under the clear coat. This technique provides a metallic finish, but it definitely looks different than the OE silver finish. Over time, heat from the engine bay will eventually yellow and crack the clear coat.

If anyone has an alternative process that looks close to the original aluminum finish, I'd really appreciate it if you could please share this information. I'd rather not powder coat as that finish is too thick. I would be open to a durable matte paint that appears like metal. I've also heard of a matte silver coating in a aerosol can, which has aluminum particles in the formula, so hopefully that would produce a visually more metallic aluminum finish. Anyone know of this product?

All suggestions are welcome and you can also PM me if you prefer! Thank You!

[TimeMachinE30]

Just powdercoat it the color you desire. Looks original..keeping that freshly cast gleam but has the durability of a good powdercoating job.

[flyboyx]

i really like the crinkle finish. black is the common color but you can find blue, red, orange, etc if you don't mind ordering on line. 2 cans are more than enough for both the manifold and the valve cover.

I've done black and red with great results.

[digger]

vapor blasting?

[ForcedFirebird]

To keep the original aluminum look, first media blast, then use a product called "Alumablast". It will look like fresh media blasted aluminum, but will fill all the pores so that every fingerprint won't be etched in forever. Just be weary that brake clean will remove it.

Second best thing I found is to media blast, then coat liberally in WD40 immediately after. This looks a touch better, but you have to keep it maintained with a light coat or it will eventually dry out.

[SkiFree]

To have a %100 correct finish you should spray the thing down with cosmoline. When these cars were new the valve covers and intake manifolds had a yellow film of cosmoline overtop. This coating would remain indefinitely, at least until some enterprising individual took a scrubber to it. A pure, bare, aluminum finish was never "original".



Here are some great M20-specific threads on it.

https://www.r3vlimited.com/board/showthread.php?t=310220

http://www.e30tech.com/forum/showthread.php?t=76093

[FredK]

Actually, wasn't cosmoline only sprayed on vehicles destined for export? My recollection, which may be wrong, is that in the European market, since cars did not have to exported via ocean cargo, they were not coated with cosmoline.

[D.Martijn]

Actually, wasn't cosmoline only sprayed on vehicles destined for export? My recollection, which may be wrong, is that in the European market, since cars did not have to exported via ocean cargo, they were not coated with cosmoline.

My Touring is from Germany and has cosmoline on it..

[FredK]

My Touring is from Germany and has cosmoline on it..

Oh man, I guess that was a faulty memory I had haha

[djjerme]

Just make sure after you media blast it - you hot tank the crap out of it. You don't want any of the media to go through the engine. If doing the valve cover, the oil baffle can hide some left over media.

Also, there is metal protection you can get that is used following an electroplating. It could be used on Aluminum, but I don't know if it seals the surface enough to prevent oxidation.

[SkiFree]

Oh man, I guess that was a faulty memory I had haha

Well, it may be a late model thing or something. I do remember reading about euro-deliveries on new M3's not having cosmoline.

[zipzam]

Hey Guys....

Thanks so much for everyone's suggestions and sharing your aluminum restoration methods, experience and possible products. Although Cosmoline protection may be very original to many imported BMWs, I think that most BMW enthusiasts still feel that it's an eye sore in the engine bay.

It appears that there's no perfect solution to reproduce the new aluminum casting look. Yes, the old school technique of using wrinkle black paint with machined logos always looks stunning, giving the motor a performance oriented feel. ForcedFirebird, thank you so much for your suggestion of using the product Aluma Blast, which sounds like the closest option to recreating that cast aluminum look. This product sound exactly what I had once heard about but could not remember the name.

Thanks djjerme, for also reminding me to be extra careful about making sure all the media blasting material has been thoroughly cleaned out of all the nooks and crannies inside the valve cover, which could be disastrous if not checked.


Thanks again to everyone for responding!

[zipzam]

vapor blasting?

Hey digger...

Can you elaborate about what Vapor Blasting is all about. I have never heard of that process. Is that a high heat steam shot at a very high PSI that cleans aluminum or removes a layer of aluminum?

Another enthusiast also mentioned using a stainless steel media blasting material which imparts some stainless into the aluminum so that it gives the surface a more metallic look. Not sure if it also has to be clear coated to protect is as well though.

[ForcedFirebird]

Well, it may be a late model thing or something. I do remember reading about euro-deliveries on new M3's not having cosmoline.

The dealers were supposed to wash it off, and it was actually clear when applied, so that may have been a difficult task to clean properly. I have found over the years, the cheaper the initial price of the model, the less likely it was washed when it got stateside. Problem is (as we all know well) if left on, it becomes very difficult to remove. If you poke around the net there's a lot of gunsmith info about it, and ways to remove it safely. Steam, elbow grease and a hard rubber scraper is all I found that removes it while keeping the paint safe.

[FredK]

Hey digger...
Can you elaborate about what Vapor Blasting is all about. I have never heard of that process. Is that a high heat steam shot at a very high PSI that cleans aluminum or removes a layer of aluminum?

Vapor blasting from what I gather suspends glass bead in low pressure water and air and shoots it at mostly aluminum parts, peening the pores mostly shut.

http://noreasterblastworx.com/vapor-blasting/