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i'm doing my valve adjustment and the covers are in bad shape. is it a issue that the covers are flaking on the inside? mine are the magnesium ones. is it ok to paint them with high temp rattle can paint?
If they are flaking on the inside, you are getting those metal flakes inside your motor...so my feeling would be to go to the rennline billet covers or hargett billet, etc...
Having them media blasted and powdercoated could be an option too. I can't imagine that rattle can paint would hold up very well being immersed in hot oil.
The only media to use would be soda, dry ice, plastic or walnut shells. My friend and go to engine builder has done a few rebuilds of ruined engines as a result of glass beading the inside of valve covers. The media embeds in the (softer and more porous) alloy, and releases after time and heat.
You can get aluminium valve cover replacements from your dealer or from eBay for a very reasonable price. I would go OEM. I bought aftermarket and they don't play well with all the studs, the valve cover is hard to push as the holes don't line up perfectly like the OE version does.
You can get aluminium valve cover replacements from your dealer or from eBay for a very reasonable price. I would go OEM. I bought aftermarket and they don't play well with all the studs, the valve cover is hard to push as the holes don't line up perfectly like the OE version does.
Pat told me he always uses factory parts because he knows they will work right.
No chance that mag would just flake apart especially covered in all that oil. Sounds as though somebody might have painted them at one time and the paint didn't adhere. There is no need to paint the inside of the valve covers and no need to blast them. You might consider a chemical strip.
Any time a magnesium part or any part is grit or media blasted it should be washed and dried immediately in an oven with circulating fans at around 160 degrees. Magnesium should be put through a chemical conversion sometimes called a DOW treatment or acid pickle to prevent corrosion and help the paint to adhere.
This is the first I have head of glass bead embedding itself into the surface and releasing later under heat. Not sure where this comes from. Glass or shot peen will do just that peen the surface. Most likely the parts were not properly cleaned before installing which would make more sense.
If they are flaking on the inside, you are getting those metal flakes inside your motor...so my feeling would be to go to the rennline billet covers or hargett billet, etc...
This!
I bought uppers and lowers from Rennline and there are amazing!
My covers were flaking on the inside. I chemically stripped the paint off and have left them bare. I did refinish the outside using an acid etch and 2k paint.
I was toying with replacing them as they had warped. I managed to sand the distortion out to a level where they seal ok, but would probably replace with 993 ones if they begin to leak again. I think the 993 ones are plastic.
I would not replace with the 993 plastic ones. I would consider using the factory aluminum versions they are made from the same tooling.
I have fixed many mag covers with some minor sanding. It is the rubber seal that prevents the leaks. You can sand them flat and save them.
Do you have any pictures of the flacking paint? I am assuming yours were painted on the inside at one time by someone? Most of the cars I work on have the aluminum covers but the cars with original mag covers both early 964 and 944 were not painted on the inside.
I would not replace with the 993 plastic ones. I would consider using the factory aluminum versions they are made from the same tooling.
I have fixed many mag covers with some minor sanding. It is the rubber seal that prevents the leaks. You can sand them flat and save them.
Do you have any pictures of the flacking paint? I am assuming yours were painted on the inside at one time by someone? Most of the cars I work on have the aluminum covers but the cars with original mag covers both early 964 and 944 were not painted on the inside.
Ok thanks for the advice regarding the plastic covers.
Yes, I too sanded my covers flatter (not completely flat) so they seal.
My car is a 1990 and the covers are mag. sadly I cannot find the images of the inside of the covers, but I'm 99% certain they were factory painted. The material was so damn hard to remove and had been on there forever. I didn't want to replace the coating, as I didn't want any more potential flaking issues inside the motor. I work in auto refinish / car restoration, so I do see lots of different coatings etc.
I'm almost too ashamed of this image, as it shows how rough my motor looked before I detailed it. But it shows the flaking finish on the outside of the cover.
Last edited by backitoff; 09-05-2018 at 07:30 AM.
Reason: Attach image
I would not replace with the 993 plastic ones. I would consider using the factory aluminum versions they are made from the same tooling.
I have fixed many mag covers with some minor sanding. It is the rubber seal that prevents the leaks. You can sand them flat and save them.
Do you have any pictures of the flacking paint? I am assuming yours were painted on the inside at one time by someone? Most of the cars I work on have the aluminum covers but the cars with original mag covers both early 964 and 944 were not painted on the inside.
Ok thanks for the advice regarding the plastic covers.
Yes, I too sanded my covers flatter (not completely flat) so they seal.
My car is a 1990 and the covers are mag. sadly I cannot find the images of the inside of the covers, but I'm 99% certain they were factory painted. The material was so damn hard to remove and had been on there forever. I didn't want to replace the coating, as I didn't want any more potential flaking issues inside the motor. I work in auto refinish / car restoration, so I do see lots of different coatings etc.
I'm almost too ashamed of this image, as it shows how rough my motor looked before I detailed it. But it shows the flaking finish on the outside of the cover.
Believe it or not the covers along with the fan are painted in Zermatt Silver. The color does change to what you see over time.
Looks like cleaning that was a decent sized job. They all flake on the outside over time. I don't believe Porsche properly prepped the surface of the mag before painting.
If you find the pictures of the inside I would like to see them. I don't believe this cover was painted on the inside but it might have been reworked at one time.
Clearly aluminum covers weren't painted inside or out. The aluminum covers are identical castings to the mag using the same tooling.
I don't think it was just Porsche having issues with the flaking magnesium covers as my Mercedes (M104) had the same issue, and I know C4 Corvettes (through 1992) did as well.
08-15-2014, 11:28 PM
valve cover question
