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Ok second post.  Any recommendations on  polishing or sealing a magnesium case prior to an engine build?  Cautions against igniting magnesium dust are duly noted.  A cast mag case itself looks a bit drab so trying to figure if it’s worthwhile to even it up a bit

and any sealing recommended due to magnesium porosity?


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Polished magnesium looks the same as unpolished.  Sort of a smooth grey.  Same for the transmission.  Painting it is a way better option.  I saw one over at Chico's here in Arcadia ca.  with a powder coat black wrinkle finish.  It was really nice looking and hid all the "flash wrinkles" on the case surface.  Of course a lot of the small mould flash had been removed or smoothed out before.

Transmissions look really good painted and then the top of the case ribs ground off and "polished"...............Bruce

Ok good advice thanks.  I already have a transmission case beautifully powder coated. Any thought on getting the case walnut or bead blasted to smooth out the castings - then Gibbs it.  It prob won’t be as visible as the tranny and I’d like to keep as much heat transfer to air as possible so I’d prefer not to powder coat or paint it.   I think I’m good with the full grey but would like for it to look less ‘flakey’ from the casting.

thoughts or experience with bead soda or walnut blasting?

If your trans is already powder coated, and it’s done well, I’d just leave it. The reason I Gibbs Brand mine is that it wasn’t and the paint was all flaking off.
Magnesium needs something, it’s very susceptible to corrosion when exposed to water and air.
Beauty is in the eye of the beholder.  The telltale signs of the casting is one of the reason I chose to protect the bare surface rather than cover it up.  

Don't sandblast, glass bead blast, walnut shell blast.  You will never get it all out of the case or even the metal.  I use baking soda blasting on wood and other soft materials.  It might be ok with flushing and rinsing with water and air pressure.  I don't think it is severe enough to smooth out those flash wrinkles though. You may have to smooth those out with some cratex tips on your air driven hand tools......Bruce

I had a trans case bead blasted by an auto electric shop. I washed it several times in a plastic tub with dish soap. I dried it with air, then put it in the oven at 250F for a half hour to drive any remaining moisture out. Primed then painted it black. I think I even cleared it. The finish still looks good about ten or more years later.

That worked out well.

Recently I did another one, but used a sand blaster. I blasted it with a pressure washer inside and out, then did the same soapy water, air, and oven treatment. Painted it all up and it's now in the race car.

I think it's important to keep moisture away from magnesium, corrosion will do you in eventually. Magnesium corrodes worse than aluminum with moisture exposure.

For an engine case I would NOT use sand, too many oil passages for debris to come back and haunt you later. But honestly a transmission case is wide open and there is no place for sand to hide. DO NOT sandblast any machined surfaces.

ok thanks. I'm going to do some hand power/air tool light smoothing manually on the case exterior and not go a blasting route.  I don't have a blasting rig anyways so I'm not comfortable with trusting someone to treat the machined surfaces with special care.

Then afterwards I'll give it a wash, light bake to dry up (I have a homemade oven cabinet that I made for powdercoating) and then Gibbs it.

I'm planning to get the fan shroud blasted so I can powdercoat to match the transmission. Anything else recommended to tastefully color sync my engine bay? I don't need to whole thing dripping in color - but I have a blue that should compliment grey's and bare metals well

This Spyder will literally be only the second NEW vehicle I will have owned in my life, so I'm sort of obsessing over things that I would typically never give a thought to.


@MikeP posted:

This Spyder will literally be only the second NEW vehicle I will have owned in my life, so I'm sort of obsessing over things that I would typically never give a thought to.


That’s what make plastic clown cars fun.

Full disclosure: When the paint started flaking off my trans, I sought the advice of a guy who does my powder coating. In a past life, he ran one of the best indie VW shops in town for about thirty years. Besides powder coating, he restores old BMW, MotoGuzzis, Puchs, etc. He showed me his immaculate 52 Puch and told me the process he used on the cases:

  • Aircraft Paint stripper to get the worst of the paint off. Aided by little wire brushes that you can get at harbor freight $2.99/20. The brass ones worked best, but the plastic bristle ones held up the longest.

  • Eagle One Magnesium Wheel Cleaner. This isn’t your fathers wheel cleaner. Wear PPE and be careful with it. Same with the paint stripper.

  • Spray it with water once it works it’s magic. Since I couldn’t put it in the oven like Danny suggests, I used a heat gun on it, a small area at a time, and got it just hot enough that I could only touch it for 4-5 seconds.

  • When that was done I used a dry brass brush to get the residue of the shell cleaner off the nooks and crannies, then I treated it with the Gibbs Brand.

I recoat it once a year and even though I rarely drive in the rain, I get caught out every once in a while and between this and infrequent washings I’ve never seen any taletell white spots on the bare magnesium.

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