For the experts... I picked up a set of valve covers advertised as original new never installed. I didn't pay allot so not too concerned as I'm gonna use them anyway however I'm wondering if they are OEM.
assuming they are the magnesium as there is pin holes, the finish is dull (clearly no polish) so just wondering if they are OEM

 

Does this help?
https://www.corvetteforum.com/forums...-question.html

M

 

Yes sir, thanks once again Mooser, I thought so, only thing I questioned was the finish as it's a little dull and appears a coating which I assume is the way the finished the magnesium

 

I always understood the 81-82 magnesium covers were all painted black with just the tops of the fins cleaned off.
M

 

yeah just never seen the silver dull finish... I'm going to like it as I have little "bling" under the hood besides air cleaner and shielding, just not a fan of the orange valve covers

 

nice engine.. not sure what your year is but the link Mooser put in references gray paint on 81 up covers.. maybe that is the gray masked then black?
depending on your year you may want strip and polish like the oem for your year L82?
i love the cast covers without worry of bending the steel ones..
black i refurbed my 79 below. that emblem is available from vendors.
https://www.corvetteforum.com/forums...ification.html

 

Those covers are aluminum not magnesium. Also those covers have been ether particle blasted in some form or tumble cleaned. Here is a photo of and NOS cover before the engine was started with them on it. Depending on what year Corvette you are talking about. Later versions were polished and painted

 

78-80 were black paint with exposed aluminum fins. The 81-82 covers were black paint finish with silver painted fins. You can't just leave the magnesium exposed on the fins or it turns dark in color rapidly. Regular paint procedures will not stick to magnesium. Specific process and special coatings required for painting magnesium parts.

The OP's covers are beautiful but they have a custom finish on them. Look to be made from aluminum based on the color of the inside. They also look to be early '80's GM produced covers based on the dual casting numbers.

 

I used a '76-'79 aluminum wheel center cap emblem on my oil cap to match the right side...


STA70972

 

The magnesium will polish up nice (but the pitting will still be there and might be more noticeable than if painted with the find polished)
M

 

looks good... I actually ordered the emblem new before knowing the valve covers came with one on there, I like the lower gloss for now, not sure how the polish will look with the cast pin holes

 

that looks good, love the polished ribs and probably gonna copy that, clean engine bay

 

Was thinking the same but i do like the polished ribs now that i see it

 

I am the one who posted the info on the finned valve covers in the 10 year old post that Mosser linked in his post above.

What you see in the surface of the covers are not "pin holes", but just casting flaws in the surface of the covers. It's really hard to tell from the pictures if the covers you have are aluminum or magnesium, but based on their color (bare magnesium has a dull gray finish with a slightly brown look to it), and the surface imperfections, I'm guessing they're 81-82 magnesium covers that have had the paint striped off of them. When magnesium is blasted, striped etc, it can open up the pours in the surface, causing the rough casting appearance your covers have. If left unfinished the surface can corrode and discolor. Also, I believe the proper way to strip and clean magnesium parts is with an acid based cleaner, since blasting with shot, glass etc can contaminate the surface and speed up deterioration.

To rehash what I posted 10 years ago, that basic cover design was used from 69-82. It was first used on the 69 Corvette 350/350, and the 69 Camaro Z/28. It was also used on 70-72 LT-1's, 74-77 L-82's, and 70-72 Z/28's. All 69-77 covers were made of aluminum, and had a polished finish. There were some differences in the mating flange of the covers used on the earlier covers, and the opening for the oil fill was different on 71-72 covers, because they used a rubber push in oil cap, but overall the 69-77 covers are pretty much the same. From 78-80 the exact same aluminum covers were used on L-82's, but were painted gloss black, with the top edge of the fins left bare, natural aluminum. As part of GM's weight saving efforts for the 81 Corvette, to meet federal gas mileage ratings, in 81 Chevrolet started casting those covers in magnesium. Because magnesium corrodes easily, the magnesium covers were painted gloss black, and the top edges were painted a dull gray. The black painted finned magnesium covers came on all 81 and 82 Corvette engines. Since the same mold was used for both the aluminum and magnesium covers, both the aluminum and magnesium part numbers were cast into the underside of the covers, starting in 81.

With both part numbers on the underside, your covers could be production magnesium covers off of an 81 or 82 Corvette, or newer service replacement aluminum or magnesium covers, though my guess is they may be magnesium. I'm not really sure how you can tell what material they are though.......except maybe setting them on fire???? (magnesium burns with a bright white flame).

If they are magnesium, you really can't polish them and leave them bare. If polished I think they best way to preserve them is to have them anodized, but even painting magnesium I'm told requires some special prep work or primer?

As I said above, if they're magnesium, they won't hold up if you leave the fins bare. This is why GM painted the tops of the fins gray on the 81-82 covers, because they knew the unfinished magnesium fins would discolor and corrode.

 

If they are not coated inside, you can take some fine sandpaper and clean off a small spot about a 1/2" or so and a drop or two of normal white vinegar on that spot, if it's aluminum it wont do anything, if it's magnesium it will react quickly and fizzle a little bit. Or take a knife and scrap a little off the inside edge and put it on a bit of folded paper and light the paper (outside), even the shavings will burn up bright, it it's aluminum it won't get hot enough to do anything

Protecting polished bare magnesium is a pain, good coating of colenite insulator wax will last most old-school wheels a couple of summer months if they don't get wet. I've heard really good things about the newer ceramic coatings and hybrids but I've never tried them. All the stuff I deal with is aluminum these days
M

 

That’s what came on my 1981,all black,except for the top of fins were shiny.

 

Thanks... It was a little more than polish....I had them chrome plated.

 

I believe they are aluminum and I don’t think they are factory… Looks like somebody powder coat them

 

Thanks all, they are on... sanded down the ribs and polished them, left the low gloss look and for now prefer it, better than the orange covers to me.

Again thanks to all.