Author Topic: Is there an good how to for the zinc dichromate finish on a Holley?  (Read 1022 times)

Kent

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Hello, I want to restore some of my holleys back to old glory and I´m not sure which chemicals I have to use to get the same finish like on the 65-70 carbs from holley. Who can help me out with that. I´m in germany and I dont want to send all my carbs arround the globe as there are some real expensive ones I was searching for years. Maybe you guys can help me out with how to´s and videos. I would need the correct procedure for the correct finish on a holley. Thanks...

Just found that at VMF
Your right that carb cleaner (and other solvents) will not remove anodizing. But zinc die cast Holley carburetors are not anodized (an electrolytic process) they are yellow chromate (ie 'Gold Irridite'). Chromate is a cold dip coating (no electrolysis). New castings with fresh chromate coatings are somewhat resistant to solvents but older castings with weathered chromate surfaces (ie 'old and grimy') the chromate is oxidized and will generally wash away especially after extended exposure to the solvent (ie 'dipping').

Is that correct? So the carbs were only put in an chemical bath without electrolysis?
« Last Edit: January 12, 2022, 12:14:24 PM by Kent »
SAAC Member from Germany and Owner of a unrestored 1967 Shelby GT500, 1968 1/2 Cobra Jet´s and some nice Mustang Fastback´s 67/68

Drew Pojedinec

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #1 on: January 12, 2022, 12:48:06 PM »
Sure. Just start doing it.
It took me 200-300 carbs to get decent.
By carb 850 I really had it consistently good.

Strip old coatings.
I do this with 90C lye/tsp mixture. Be aware, too long will destroy the casting.
Use an mild acid to activate and neutralize the bases. Be aware, too long will destroy the castings.
Dip in a standard yellow chromate. Time and temp are depending on your chromate recipe.

You can use the old publicly available Chronak process. Or buy a ready made one.
Tho to be honest, if you are in EU likely hex chromates are probably not attainable.

You can also make your own yellow for castings. This works better than Chronak process.
200mg sodium dichromate, 200ml sulfuric
Be aware this will heat up to 160C nearly instantly and is incredibly dangerous, kinda eats unexposed flesh. .
Rinse chromate crystals with nitric while vacuum filtering.
This makes chromic acid.  Be aware it is a powerful oxidizer, so best to do with with sealed containers and a fume hood.
Use that chromic acid and find a ratio with nitric and sulfuric that works well for you.
Your brown/grey/yellow/iridescent looks depend upon your chromic to sulphate ratio, so experiment.
Also be aware that there is an expensive and involved process to dispose of hex chromates… basically you need to turn them to the trivalent state etc.
Took me 3-4 years a s probably $12,000 to get my setup working well.

The best chromate book is by Biestek, I bought a copy in Frankfurt actually.

Good luck!

Drew Pojedinec

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #2 on: January 12, 2022, 12:54:42 PM »
To redo the hardware you need to make a zinc plating bath.
Involves doing the electroplating and passivating in a chromate.
To do a holley hardware properly you need four different chromates.

I would suggest using Acid Chloride zinc bath. It’s more difficult but much safer than cyanide based solutions.

My bath consists of Zinc, ammonia, and potassium chloride. You’ll need to also add makeup and maintenance brighteners. Typically these are best attained from large suppliers, but you can buy from Gateros in small batches (based in the UK).

A decent plating station will take up 2x3 meters of shop space and cost roughly $2-3,000 to makeup. Maintenance doesn’t cost as much, but if you intend to keep the same solution you’ll need to regularly adjust ph, titrate for chlorides and titrate for zinc content.

Best book is “Zinc Plating” by Herb Geduld… you can normally find a copy for $200-$300.

Lemme know if you need recipes for this, but you’ll have to attain your own brighteners.

Drew

Kent

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #3 on: January 12, 2022, 01:24:49 PM »
Ok that is a lot of info thank you for that. I was hoping there is an "easy" way to dip them and get them close to good/ correct. How long does your coating last or better question if I put the carb in a ultrasonic cleaner will it get off? Because thats what usually happen with holley and other carbs as you maybe know? Maybe I should send you my carbs, where are you located? Maybe next time when I´m in the states I can bring them arround.
SAAC Member from Germany and Owner of a unrestored 1967 Shelby GT500, 1968 1/2 Cobra Jet´s and some nice Mustang Fastback´s 67/68

Drew Pojedinec

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #4 on: January 12, 2022, 01:38:02 PM »
My most recent coatings (within the last 1-2 years) are very durable.
I spent a lot of time trying to destroy them.

A lot has to do with the original casting quality.
Zamac3 is very porous, so impurities get in and make it harder to take a fresh coat.
Corrosion also makes it harder to get a proper coating.  I mean, these are 50-60 years old.

If you are ruining the coatings in the ultrasonic, you need to research better cleaners. I cannot suggest one in the EU, but milder is better.

If there was an “easy” way to do this properly, everyone would be doing it.

I live in Georgia US.
I do ship all around the world. Most recently DHL has provided very good reliable service, tho expensive.

I tried to attach photos, but I’m in the south atlantic with weak cell service. My AirFuelSpark fb page has lotsa photos of the work done.

poboy427

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #5 on: January 12, 2022, 06:49:42 PM »
Drew was chosen to do the Holley carb on 5R002. That bout says it all.

Ray
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Drew Pojedinec

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #6 on: January 12, 2022, 09:45:19 PM »
Drew was chosen to do the Holley carb on 5R002. That bout says it all.

Ray

Was my pleasure to do 003.

deathsled

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #7 on: January 12, 2022, 09:53:01 PM »
I didn't even know who Drew was until this thread.  That said, he did 5R002 from what I gleaned from this post.  How can there be any other rational choice other than to choose Drew?  This is not a paid sponsorship either.  Don't forget the origin of 5R002 least we forget.
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Drew Pojedinec

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #8 on: January 12, 2022, 10:57:21 PM »
Don’t believe I did the carb for 002 unless they didn’t tell me what it went on (that happens a lot).
I did do 003 and that was good fun.

Anyway, happy to teach stuff like plating. Even started a fb group so us hobby guys can share.
Castings are a LOT of trial and error tho. It really can’t be taught, so mich goes by “feel” if that makes sense.
Even if I told you my process step by step it’d still take forever to get it even decent.


Picture of a Boss carb I did last time I was home. It’s really neat to keep the cars and parts alive 50-60 years later.

(Also not an advertisement, I do this for fun)

shelbymann1970

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #9 on: January 13, 2022, 07:19:06 AM »
Don’t believe I did the carb for 002 unless they didn’t tell me what it went on (that happens a lot).
I did do 003 and that was good fun.

Anyway, happy to teach stuff like plating. Even started a fb group so us hobby guys can share.
Castings are a LOT of trial and error tho. It really can’t be taught, so mich goes by “feel” if that makes sense.
Even if I told you my process step by step it’d still take forever to get it even decent.


Picture of a Boss carb I did last time I was home. It’s really neat to keep the cars and parts alive 50-60 years later.

(Also not an advertisement, I do this for fun)
I love your FB page Drew. You are very generous with your knowledge. Even though I got a great local guy(who I never met) do my last 2 M-code 69 Holleys with great success I recommend you to everyone who needs carb work as my local guy does not do carbs for everyone. I got mine done through a mutual friend. Bolted one on my 428SCJ and it runs great without any tuning needed(pre tested before I got it by the rebuilder). Carb 1 on car. Second carb in pics. Gary
« Last Edit: January 13, 2022, 09:44:45 AM by shelbymann1970 »
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j427

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #10 on: January 24, 2022, 12:08:23 PM »
I have known Drew for a while. We both are in Ga. A good looking carb is only half of it. Wow that's pretty does not make it run. He go's where most have never gone before with Ford Holley's. My self I would trust him with the rarest Ford Holley in the world. Wait he has done all of them. LOL Drew I will send you a bill for this good word. LOL   Keep up the best work.
Jack in Ga

shelbymann1970

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Re: Is there an good how to for the zinc dichromate finish on a Holley?
« Reply #11 on: January 24, 2022, 12:31:21 PM »
I have known Drew for a while. We both are in Ga. A good looking carb is only half of it. Wow that's pretty does not make it run. He go's where most have never gone before with Ford Holley's. My self I would trust him with the rarest Ford Holley in the world. Wait he has done all of them. LOL Drew I will send you a bill for this good word. LOL   Keep up the best work.
Jack in Ga

I recommend all to Drew. The guy who I used on my last 2 428CJ M-code good date coded Holleys did a fantastic job. I did nothing when I bolted it on my 428 SCJ and fired it up and the car hadn't run in 6 years(he test runs them). Still have done nothing so far and it was put on in June. I'm lucky because the guy who did mine just doesn't take on any customers and does Gm Ford carbs he buys and sells them at swap meets but has been doing BBF carbs for a good friend of mine for years now with zero complaints. I never thought locally I would be able to replace Mike Reimeschneider(RIP). Now I need a distributor guy...... Gary
Shelby owner since 1984
SAAC member since 1991
1970 GT350 4 speed(owned since 1985).
  MCA gold 2003(not anymore)
1969 Mach1 428SCJ 4 speed R-code (owned since 2013)