Author Topic: Rochester carb plating  (Read 2248 times)

Offline cobrajet_carl

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Rochester carb plating
« on: December 06, 2015, 12:14:58 AM »
Was hoping to find out what the original platings were on the 1971 Rochester Quadrajet carb. Original seems like no plating on the main body but it may just be worn off.
Carl
70 and 71 Dearborn mach Is

Offline J_Speegle

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Re: Rochester carb plating
« Reply #1 on: December 06, 2015, 03:00:48 AM »
Believe the bodies were dyed similar to what was used on the same pot metal of the Holley's .

Check out some of the Camaro restoration sites - for examples

Don't have any NOS ones (for pictures) in my files but a number originals have that same goldish finish. Its likely the others have simply lost the dye job from the elements and years passing   

Will look at the one out in the garage tomorrow to see what condition the coloring is on that one
Jeff Speegle

Anything worth doing is worth doing concours ;)

Offline Bob Gaines

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Re: Rochester carb plating
« Reply #2 on: December 06, 2015, 03:03:29 AM »
Believe the bodies were dyed similar to what was used on the same pot metal of the Holley's .

Check out some of the Camaro restoration sites - for examples

Don't have any NOS ones (for pictures) in my files but a number originals have that same goldish finish. Its likely the others have simply lost the dye job from the elements and years passing   

Will look at the one out in the garage tomorrow to see what condition the coloring is on that one
+1 . same same.
Bob Gaines,Shelby enthusiast, Shelby collector , Shelby concours judge SAAC,MCA,Mid America Shelby

Offline WT8095

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Re: Rochester carb plating
« Reply #3 on: December 06, 2015, 01:08:05 PM »
The yellowish color is not really a "dye", it is a chromate conversion coating. Chromate is used as a final treatment on zinc and cadmium. The carburetor body is a cast zinc alloy, so it will end up a somewhat dull finish when chromated, whereas the steel hardware parts will end up shinier and brighter after chromate because they were zinc (or cadmium) plated first, which is a shinier surface than cast zinc.
Dave Z.

'68 fastback, S-code + C6. Special Paint (Rainbow promotion), DSO 710784. Actual build date 2/7/1968, San Jose.
'69 Cougar convertible, 351W-2V + FMX, Meadowlark Yellow.

Offline J_Speegle

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Re: Rochester carb plating
« Reply #4 on: December 06, 2015, 04:40:35 PM »
Believe today the restorers are using a dye to reproduce the original look. Had a couple of quarts of the stuff around the house before the last move. Can't recall the supplier or the fancy name of the stuff.
Jeff Speegle

Anything worth doing is worth doing concours ;)

Offline WT8095

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Re: Rochester carb plating
« Reply #5 on: December 06, 2015, 05:56:59 PM »
Believe today the restorers are using a dye to reproduce the original look. Had a couple of quarts of the stuff around the house before the last move. Can't recall the supplier or the fancy name of the stuff.

There are multiple options for chromating these days, it can get a little complicated and the terminology can be confusing. There's the old process, which used hexavalent chromium, which is now identified as a hazardous substance and is not allowable for RoHS compliance. That doesn't mean it's not available - just that most companies are not going to use it in commercial products. Hex chrome over zinc will give the nice yellow finish we're used to seeing.

To replace hex chrome, trivalent chromium is now being used. It can give either a clear (bright silver) finish, or a classic yellow. There are different proprietary methods for achieving the yellow, however. Some use a pigmented solution (which may be where the "dye" reference comes in). Some topcoat with a yellow color. And some use a process that will finish yellow without pigment or topcoat. The trivalent methods do not necessarily provide the same level of corrosion protection as hex chrome, however I have read reports that some do and that the technology is improving in this area.

Briefly, zinc (or cadmium, in the past) is used to protect steel. It provides sacrificial protection from galvanic corrosion. Chromating is a top barrier to prevent the zinc from corroding. a sealer coat can even be applied after both of those to provide further protection, but I don't believe this was used on automobiles of the vintage we've dealing with. For driven cars or those in humid climates, corrosion protection is an important consideration when selecting a refinishing process. For those in arid climates, appearance may be the only consideration, and a coating that has the same cosmetic appearance as the original may be a legitimate choice.
« Last Edit: December 08, 2015, 09:07:58 AM by WT8095 »
Dave Z.

'68 fastback, S-code + C6. Special Paint (Rainbow promotion), DSO 710784. Actual build date 2/7/1968, San Jose.
'69 Cougar convertible, 351W-2V + FMX, Meadowlark Yellow.

Offline cobrajet_carl

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Re: Rochester carb plating
« Reply #6 on: December 08, 2015, 12:19:58 AM »
Check out some of the Camaro restoration sites - for examples

Can't believe I didn't think of that ! :-[ Funny only Brand-X I have is a 427  Holley 3130...
Carl
70 and 71 Dearborn mach Is