C1 Plating of coarse and fine thread bolts

[Ian G.]

In the new book by Tom Howey and Bob Baird of NCRS titled "1958-60 Corvette Restoration" they say the following about bolt plating:

*Generally, coarse thread bolts are Cadmium plated
*Generally, fine thread bolts are Black Phosphate plated.
*Exceptions are Grade 5 and 8 coarse thread bolts are generally Black phosphate plated.

Does this sound accurate? If so, can folks identify some exceptions?
My car only came with about half of its original bolts and I plan to plate all my repop bolts and hardware.

For instance, would the clutch return spring bracket sems bolts (3/8-fine 1/2") be Black or Cad? I can't find anywhere where those bolts are identified. Paragon delivers them in zinc.

Were there any bolts Zinc plated as a standard? I know they don't cad plate generally now due to environmental concerns.

Sorry for all the questions, but I'm spending a lot of time currently separating bolts and brackets for plating.

[Bruce B.]

Re: C1 Plating of coarse and fine thread bolts

Ian,

I think "generally" is a wide open term.

As an example the B & H bolts holding the 57 and 58 fuel filter canister to the bracket are 5/16-24 (fine thread) and are cad plated.