Holley Carb. plating

[68goat]

Which method would one use in replating a Holley carburetor to the original finish, which is a gold irridite type finish. Also, are these carbs aluminum or pot metal??

[mcaswell]

Yellow chromated zinc plate - see http://www.caswellplating.com/kits/zinc.htm

Carbs are usually zinc die cast.

[68goat]

surface prep

What type of surface prep is preferred for this, (ie) polished, glass bead blasted or tumbled with ceramic media??

[mcaswell]

If you want a shiny surface, you need to polish first. If you want a satin finish, glass beading works well. Either way, as long as the part is clean, zinc will apply readily over existing zinc.

[shoprat]

Re: Holley Carb. plating

How big a kit would be required? What is the physical size limitations of the 1.5 gal kit?

[dfarning]

Re: Holley Carb. plating

If you want a satin finish, glass beading works well. Either way, as long as the part is clean, zinc will apply readily over existing zinc.

If you bead blast zinc die-cast, you may want to put the part in a pan of boiling degreaser after blasting. Maybe I am working with older (and poorer) die-cast than your holly, but I have noticed that bead blasting tends to embed glass beads in the casting surface. I use #80 glass beads at 50-60 lbs of air pressure.

A good rolling boil seems to work out the beads pretty well. If the part has taken on beads, you will get a fine sandy layer on the bottom of the degreasing pan within a minute or two. The sandy looking stuff is cracked beads.

I like to lift the part out and let it drain several time at different angles to rinse the beads out of the jets. Seems to work better than trying to blow out each jet individually with high presure air.

Keep us posted on your results. There are a few of us working with carbs.

[customcab]

Re: Holley Carb. plating

Hi. First time poster here and I too have a question concerning a Holley Carb. I want to restore the original coloring to the body and bowls. The carb is in good condition but the color is gone. It had some very light scaling in the top surfaces, which I bead blasted to clean. Are there any other cleaning or prep steps that are critical before dipping in the yellow cromate?

Thanx, Phil

[awdmh]

Re: Holley Carb. plating

I'm new and curious, also. I have the chromate, is it necessary to replate? Other than blasting, what steps are needed before the dip in chromate. thanks!

[dfarning]

Re: Holley Carb. plating

If I have a good layer of zinc for the chromate to adhere to I just activate with an acid dip for a few seconds. If the zinc does not look good I put down a thin layer of zinc before the new chromate.

Dave

[awdmh]

Re: Holley Carb. plating

What kind of acid?

What kind of container do you put the chromate in?

What temperature do you use for the chromate?

What ratio of distilled water to chromate? The container info was vague.

[dfarning]

Re: Holley Carb. plating

What kind of acid?

I have had the best luck with some of the commerical phospharic acid products. Now I am use metal prep from a local autobody shop. In WI phosphoric acid seems to be illegal to sell so it is pretty had to findl.

For some reason phospharic acid works nice and slowly on zinc die-cast. I have also used a 20:1 muratic acid dip at room temp, but you really need to get the part out quickly and dried.

What kind of container do you put the chromate in?

Now I am using a 3.5 gallon plastic tank.

[seanc]

Re: Holley Carb. plating

What kind of acid?

Nitric is best, but can be difficult and/or costly to obtain. IF you have to have it shipped, there's a $25 hazmat fee on top of the shipping charges.

Otherwise, muriatic or sulphuric acids work, just not as well.

What kind of container do you put the chromate in?

Polypropylene or polycarbonate. I use paint mixing buckets available from local hardware stores. Pint, quart and gallon sizes are available.

What temperature do you use for the chromate?

80? for yellow. Most chromates specifiy a range, usually 70-90?, but it depends on the particular chromate.

What ratio of distilled water to chromate? The container info was vague.

Depends on the chromate, which do you have? Mine was quite clear concerning mix ratio.

Sean

[awdmh]

Re: Holley Carb. plating

What ratio are you using? The yellow crystal chromate says to use .5 - 2 oz per gallon of water. I was wondering what ratio you use, since your pieces look so good. Thanks!

[seanc]

Re: Holley Carb. plating

I'm using the 1 oz/gal ratio.

I experimented a little w/the 2 oz mix, but found that either works the same, just depends on immersion times.

eg, 20 seconds in a 2 oz mix and 40 seconds in a 1 oz mix look identical.

The weaker mix just gives me more precision over immersion time.

Sean

[dfarning]

Re: Holley Carb. plating

Sean,
Have you tried phophoric acid as an etch and prefer nitric acid becuse you didn't like the results because phophoric it is hard to come by.

Dave