1970 Brake Bleeders

[Stephen B.]

On page 104 of the 1970 to 72 judging manual, the manual states that the brake bleeders are zinc plated. Is this yellow in color or silver?

[Jack H.]

Re: 1970 Brake Bleeders

Zinc is silver in color. If after plating, the part is dipped in chromatic acid, it takes on either a yellow 'rainbow' or dull gold hue (depends on the strength of the chromatic acid and the time the part is washed). That is called a dichromate, gold dichromate or irridite finish.

It's done to enhance the longevity of the cad/zinc plating. The gold tone is typically a THIN coating that's easy to remove by handling, polishing or simple acid etch to get to the underlying cad/zinc...

[Joe L.]

Re: 1970 Brake Bleeders

Bunky----

The bleeders were "silver" zinc.

[Joe L.]

NOS Example

Here's an example of an NOS bleeder valve:

[Wayne M.]

When did they go from 5/16" hex to 3/8" ?

This is probably an original 5/16" hex bleeder on my late '65 "905" inboard rear caliper, removed from car in 1989.

[Joe L.]

Re: When did they go from 5/16" hex to 3/8" ?

Wayne----

I believe that the change occurred sometime during the 1969 model year. They changed again during the 1981 model year (to metric).