C3 caliper rebuild

[Michael L.]

Guys,

I'm restoring my calipers and getting ready to paint them semi-gloss black. I have read in the archives that the machined surfaces were not painted since they were machined after painting. What are these machined surfaces? I'm guessing there are a total of five: the two areas where the calipers are bolted together, the two areas were the calipers are bolted onto the chassis, and the area where the brake line goes in. Is this correct? Also, if the area where the calipers are bolted together were machined after painting, does that mean that the bolts that hold the calipers together should not be painted? What is their finish then? If I elect to take these bolts out to paint the calipers, can I do damage to the caliper? The TIGJM states that the bleeder screws are zinc plated. How do I know if my bleeder screws are zinc plated? The ones on my calipers look like they have a chromate (gold) portion. Is this the zinc plating?

Thanks for your help.
Mike

[Joe L.]

Re: C3 caliper rebuild

Guys,

I'm restoring my calipers and getting ready to paint them semi-gloss black. I have read in the archives that the machined surfaces were not painted since they were machined after painting. What are these machined surfaces? I'm guessing there are a total of five: the two areas where the calipers are bolted together, the two areas were the calipers are bolted onto the chassis, and the area where the brake line goes in. Is this correct? Also, if the area where the calipers are bolted together were machined after painting, does that mean that the bolts that hold the calipers together should not be painted? What is their finish then? If I elect to take these bolts out to paint the calipers, can I do damage to the caliper? The TIGJM states that the bleeder screws are zinc plated. How do I know if my bleeder screws are zinc plated? The ones on my calipers look like they have a chromate (gold) portion. Is this the zinc plating?

Thanks for your help.
Mike

Mike-----


There are more machined surfaces than just the ones you described. However, it's hard to describe them all. It's very easy to discern a machined surface from a a rough-cast surface, though. So, if you inspect the caliper halves carefully, it should be no problem to learn which surfaces were machined and, thus, unpainted. The unpainted surfaces had only a natural steel finish and rusted very rapidly (except, of course, the surfaces where the caliper halves join).

The bolts retaining the caliper halves were not painted as they were installed when the caliper was assembled. They were phosphate-finished bolts of GM 300-M material (6 lines) and trimmed (i.e. "non-indented") hex head.

You could remove these bolts, if you wish. However, they are torqued to a very high ft/lb value (130 ft/lbs, as I recall) and they must be re-torqued to that value after re-installation.

[Michael L.]

Re: C3 caliper rebuild

Joe,

It seems that many of the surfaces don't matter when restoring a caliper because they can't be seen when the caliper is assembled and bolted to the car. I will carefully look the caliper over and keep the paint off of the areas where there is a visible machined surface. I think I will not try to remove the bolts and will just remove the paint around it and then use some flat paint to mimick the phosphate finish. What do you think?

Mike

[Joe L.]

Re: C3 caliper rebuild

Joe,

It seems that many of the surfaces don't matter when restoring a caliper because they can't be seen when the caliper is assembled and bolted to the car. I will carefully look the caliper over and keep the paint off of the areas where there is a visible machined surface. I think I will not try to remove the bolts and will just remove the paint around it and then use some flat paint to mimick the phosphate finish. What do you think?

Mike

Mike----


It's probably better than nothing, but as far as the bolt heads go, the paint won't fool any judge (assuming these are even judged, at all).

[Patrick H.]

Re: C3 caliper rebuild

The calipers are judged for "unpainted surfaces", or shall I say "growth of paint onto machined surfaces." So, it is possible to tell and we do check.

Below are pictures of NOS caliper halves. I took these pictures last year just to capture what is - and is not - painted vs. machined.

Recently I had to rebuild the calipers on the front of my 72. I painted them all in black (disassembled, tape covering the holes and the mating surface) using brake caliper paint from VHT. I then masked the black and painted the "machined" surfaces that might be visible in judging using a paint from Eastwood that "sort of" is the correct color. No, it won't fool anyone who looks very close, but it's better than not painting the areas and getting rust.

FYI, using the brake paint and then baking at 325 for 30 min gives you a very hard finish that won't wipe off with brake fluid. Nice!





Below is a picture ( I cropped it out of another pic, so it's fuzzy) of my "faux finish" painted caliper.

[Alan S.]

Re: C3 caliper rebuild

Nice pictures Patrick... Thanks!
Regards,
Alan