Polishing 71 C3 smooth aluminium valve covers

[Daniel B.]

The valve covers on my 71 LT1 are dirty and tarnished. The covers are smooth aluminium with 7 raised ribs on the top. Is there any way to restore the shine? The aluminium covers on my C2 would not polish because of the rough surface, but since these are smooth I am hoping they can be rejuvenated.
Thanks
Dan

[Joe L.]

Re: Polishing 71 C3 smooth aluminium valve covers

The valve covers on my 71 LT1 are dirty and tarnished. The covers are smooth aluminium with 7 raised ribs on the top. Is there any way to restore the shine? The aluminium covers on my C2 would not polish because of the rough surface, but since these are smooth I am hoping they can be rejuvenated.
Thanks
Dan

Dan------

C1 and C2 aluminum valve covers were as-cast aluminum. 1969 L-46 valve covers were, too. However, the 1971 and later LT-1 and L-82 valve covers were polished aluminum. You can restore the original appearance using a good aluminum polish and a buffing wheel. Or, you can have it professionally done. By the way, no polishing was done between the ribs.

[Ron G.]

[Joe L.]

Re: Polishing 71 C3 smooth aluminium valve covers

There are several methods and chemicals that can be used to remove stains from the covers in question, but if you’re going the factory assembly line appearance route, remember they were not shiny, they had a dull sheen to them. Also, it was not uncommon to see Silver paint because the covers are installed at the end of the engine paint assemblyline after the orange paint was applied when they tried to cover up most of the orange overspray on the aluminum intake manifold. Varing degrees of the silver paint will be on the very inboard of the valve covers because they were not mast off completely.

Ron------


Well, I don't know what you mean by a "dull sheen" but I can offer this: the 1969 L-46 valve covers were natural, as-cast, and quite "dull". These valve covers also had drippers on the inside upper surface. They were GM #3932415, LH, and GM #3932416, RH.

The 3932415 and 3932416 were discontinued in March, 1970 and replaced by, respectively, GM #3965541 and GM #3965542. I bought a set of these in mid 1970 to replace the steel valve covers on my 1969 300/350. The 3965541 and 3965542 were the 1970 LT-1 and L-46 valve covers. I recall that these valve covers were polished. In fact, I could see traces of a polish that looked similar to Simichrome that had gotten flung by the buffing wheel between the ribs.

In June, 1971 the GM #3965541 was replaced by GM #3990994. The latter was the "rubber plug" oil fill left side cover used in PRODUCTION for 1971-72 LT-1. It so happened that I cracked my left side cover in 1972 and when I purchased a replacement at that time it was the "rubber plug" GM #3990994. I was not too happy but that's all I could get at that time. In any event, the 3990994 was also polished.

In August, 1973 the 3990994 was discontinued and replaced by its predecessor, the GM #3965541 with twist cap oil fill. About 1976, or so, I became totally fed up with the "rubber plug" oil fill and purchased a GM #3965541. It was polished, just like the previous aluminum valve covers I purchased.

Of course, all of the above valve covers dull over time. However, out-of-the-box and, presumably on the cars when delivered, they were polished. They were not polished to a mirror-like finish but they were polished and to my reckoning "shiny".

[James G.]

Re: Polishing 71 C3 smooth aluminium valve covers

Joe, are you sure about the 69 L46 covers having drippers? I distinctly remember my 69 L46 did not - additionally I have restored countless 69 Z28's, every one has GM #3932415, LH, and GM #3932416, RH. - die cast numbers 3932417 3932418 and they have also been sans drippers.

[Joe L.]

Re: Polishing 71 C3 smooth aluminium valve covers

Joe, are you sure about the 69 L46 covers having drippers? I distinctly remember my 69 L46 did not - additionally I have restored countless 69 Z28's, every one has GM #3932415, LH, and GM #3932416, RH. - die cast numbers 3932417 3932418 and they have also been sans drippers.

James-----


My brain must be working "in reverse". The 1969 covers DON'T have the drippers; later covers do have them.

[Ron G.]

[Joe L.]

Re: Polishing 71 C3 smooth aluminium valve covers

Joe,

I don’t mean dull, what I was trying to say is they do possess a sheen, but they are not polished like chrome. Maybe if you bought them over the counter, it’s possible that they could be brighter than what was on the car when it came off the the line. Again, my opinion is that they do have a sheen but not very shiny like they were polished with a buffing wheel. - Ron

Ron-------

I expect that the SERVICE version of the valve covers was the same as those used in PRODUCTION. As I mentioned, the covers I received were obviously polished and somewhat shiny with even some remnants of the polish visible between the ribs. I have no doubt these were polished with a buffing wheel. They just looked like that kind of a polish. If they had not been polished, then I expect they would have had a finish just like the 1969 covers.

The thing is that the the shiny appearance does not last too long after the covers are installed on the engine. It rather quickly degrades to the smooth, rather dull finish which I think is what you are describing. Unless one is an original owner of an L-46, LT-1, or earlier L-82 or has purchased these covers in SERVICE when they were available, one might just assume that the way they appear now is how they always appeared. I'm virtually certain that is not the way it was "in the beginning".

The later aluminum covers used for 76-77 L-82 and SERVICE for earlier, GM #474207 and 474208, I believe were coated or otherwise sealed in some way to preserve the polished appearance.

[Joe L.]

Re: Polishing 71 C3 smooth aluminium valve covers

A correction to my most recent post above:

The GM #474207 and 474208 valve covers were never used in PRODUCTION. The GM #3965541 and 3965542 were used in PRODUCTION from 1970 through 1977 (except for the "rubber plug" style GM #3990994 left side cover for 1971 and possibly early 1972). The 474207 and 474208 replaced the 3965541 and 3965542 in early 1980 for SERVICE of all 1969-77 L-46, LT-1, and L-82. I believe the 474207 and 474208 have some sort of a coating or sealer to preserve the polished finish. Otherwise, as far as I can discern, they are the same as the covers they replaced.

[James G.]

Re: Polishing 71 C3 smooth aluminium valve covers

This is a photo of a pair of NOS OTC finned aluminum valve covers I have had for a while...
Whether they are mid 60's or early 70's I do not know... however this is the finish I have taken as original die cast and thus correct for valve covers tail shaft housings and 4 speed side covers.

[Joe L.]

Re: Polishing 71 C3 smooth aluminium valve covers

This is a photo of a pair of NOS OTC finned aluminum valve covers I have had for a while...
Whether they are mid 60's or early 70's I do not know... however this is the finish I have taken as original die cast and thus correct for valve covers tail shaft housings and 4 speed side covers.

James------


What is the part number of these covers? I can't see it in the photos.