Unpainted, machined areas on 65/66 brake calipers; A questionable area

[Gary B.]

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For the outer half caliper at the top, I masked off the flat topped mountain shape at the center between the two pistons. For the inboard caliper half at the bottom, I forgot about that area when masking. But I think I need to remove some paint which would create a double mountain peak shape that you can envision on the lower caliper half. But before I remove the paint from that area, I want to confirm that that area was indeed machined and not as-cast. In the close-up photo of that unpainted area on the outboard caliper half, I think you can see vertical machining lines. And I think the same is true on the inboard caliper half.

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[Patrick H.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

I've posted these NOS caliper halves before:

[Gary B.]

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[David B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Gary,
Just curious where info on painting calipers first shows up?

[Gary B.]

[David B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Gary,
Thanks for response, I think Joe's observation are the same for 65 & 66. Delco caliper prints only reference the following: "Coat all external surfaces with DM-6034 before machining" Not sure what DM-6034 refers to.

[Gary B.]

[David B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Your right Gary it is wild speculation, Coil springs were sprayed or dipped with "Lucas rustproof #635 compound or equivalent".

[Larry E.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Gary: Just curious when all done and installed will you be using DOT#3(Regular Brake Fluid) or DOT#5(Silicone Based Fluid)?
Larry

[Gary B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Your right Gary it is wild speculation, Coil springs were sprayed or dipped with "Lucas rustproof #635 compound or equivalent".

Wild speculation shot down again. Oh well.

Gary

[Gary B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Gary: Just curious when all done and installed will you be using DOT#3(Regular Brake Fluid) or DOT#5(Silicone Based Fluid)?
Larry

Larry,

The whole point of my swapping out O-rings in never-used, resleeved calipers is so that I know exactly what material my new O-rings are made of (peroxide-cured EPDM) and that I can safely use DOT 5/Silicon fluid.

Gary

[Gary B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

Gary,
Thanks for response, I think Joe's observation are the same for 65 & 66. Delco caliper prints only reference the following: "Coat all external surfaces with DM-6034 before machining" Not sure what DM-6034 refers to.

David,

Do you know of any other Corvette parts that were treated with DM-6034 that might give us an idea what finish it imparted?

Gary

[Kenneth B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

The castings were dipped in paint at the foundry, shipped to the machining plant & paint was only removed on machined areas only. This was true for all years.

[Gary B.]

[Kenneth B.]

Re: Unpainted, machined areas on 65/66 brake calipers; A questionable area

I’m in the process of correctly detailing the brake calipers on my ‘66. My car did not have its original calipers when I bought the car, and there was a hodgepodge of calipers on it with incorrect casting numbers. So I bought a set of resleeved calipers with correct 65/66 casting numbers from one of the brake caliper resleeving companies. But I didn’t know at the time to ask for their NCRS/Bloomington service with the correct semi-gloss paint and with the machined areas unpainted. So, I’m going to fix those issues.

For the most part, I can tell what areas were machined and therefore devoid of paint. But there is one area I’m not 100% certain of. In this first photo, the right front caliper halves are shown, showing the surface that would face the ground.

[ATTACH=CONFIG]122193[/ATTACH]

For the outer half caliper at the top, I masked off the flat topped mountain shape at the center between the two pistons. For the inboard caliper half at the bottom, I forgot about that area when masking. But I think I need to remove some paint which would create a double mountain peak shape that you can envision on the lower caliper half. But before I remove the paint from that area, I want to confirm that that area was indeed machined and not as-cast. In the close-up photo of that unpainted area on the outboard caliper half, I think you can see vertical machining lines. And I think the same is true on the inboard caliper half.

[ATTACH=CONFIG]122194[/ATTACH]

The thing that puzzles me is the other machined areas have machine marks in the form of circles or partial circles. As would be created with an end mill or fly cutter. But the two areas I’m questioning have parallel machine marks. Like would be created with a broaching tool.

What are people’s opinions about those two areas in question on the lower caliper surface, between the pistons? Machined and therefore unpainted? Or not machined and therefore painted?

Thanks,

Gary

I believe that area is the gate pad where the iron runs in the mold cavity. it is broke off and snag ground. It would be painted as it was ground before it was dipped.