What’s the best advice for polishing the valve covers on my 3.8 engine? Can they be polished, or do they just need to be replated? What finish is it, nickel plating? It doesn’t appear to be chrome, am I correct?
Brian
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Cam covers are aluminium and just need polishing with a good metal polish, finished with corn starch.
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What’s the cornstarch for?
FWIW - I like Simichrome polish… Seems to work better than the myriad of other stuff I’ve tried
It depends how messed up they are. A little tarnish will come out fine with something like Mother’s. If they’re scratched or pitted though they’d need more aggressive polishing with a wheel and rouge. I used very fine wet paper lubricated with wd40, followed by Mother’s.
Never tried it but it is supposed to be the final touch to really bring up the shine.
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They are solid cast aluminum, so the surface can be refinished and then polished depending on how far gone you originals are. Here are photos of some before and after polishing.
Before:
After:
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Corn starch acts as a final rouge, and removes 100% of that icky black aluminum oxide.
There’s a bit in this video of mine about 11 mins in on what I used. And later videos show the cam covers polished
Not having any corn starch around I tried baby powder. That works too
Well that would be soooo gentle 
And yer cam covers smell like a baby’s butt!
If you polish them with a powered wheel make sure you don’t overheat and warp them.
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Actually, our polisher heats them up to where you have to wear welders gloves to do the final buff. It works a lot better hot. When cold, the buffing compound just globs up. I guess it depends on what you are using to polish them up with. On Johns cam covers, it took a lot of sanding and grinding long before any buffing compound was used. With the sandpapers available now, you can get it up to a satin sheen so the compound does not cut much and cause ripples.
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As many have noted, there is no one solution, as original condition and how far you are willing to take it both come into play. Here is a 4 part youtube series I did for a Jaguar club tech session.
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One problem you will run in to is that doing processes like sanding and buffing on the relatively open surfaces of the valve cover where there is good access goes pretty well. But there are of course more intricate details in the covers that are impossible to reach with a big buffing wheel as shown in my video. There you need smaller felt “bobs” that can work in the tight areas. It can get time consuming in a big hurry, especially if you are going for that mirror finish look. Also, aluminum will start to form a protective corrosion layer pretty quickly, which is not shiney, so you need to get a wax or polish on there to separate your shiney aluminum surface from the air. If you were willing to accept a “frosted look” as obtained with blast cabinet media such as glass beads or walnut shells, you will be done in under an hour. If you need a mirror finish, god only knows how long it will take.
That is why you may want to embrace the spirit of the JCNA Concours guide, which states the following.
VI.B.4 Smoothing and bright polishing of originally unplated, uncoated, or unpainted metal
components (such as early aluminum cam covers and manifolds) is allowed but will be
given no extra credit. A component, whose original paint, plating or coating of zinc,
nickel, cadmium, yellow chromate, etc., or whose original sand-cast-like coarse
finish, has been removed through polishing, or other processes, shall be assigned a
non-authentic deduction.
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Very useful videos Harvey, thanks for posting.