67 Hold Off valve finish

[Mike S]

  I received the rebuild kit posted here last week from Muscle Car Research and upon cleaning the original hold off valve parts I noticed the round cover finish looks to be a gray phosphate type of finish. When dry it looks like the gray finish on my 45 ACP. In the images below you can see the interior gray finish as well as its extension into the flat machined edge. On the exterior you can clearly see the remaining gray finish in the machine mark rings. This leads me to believe the cover did in fact have a gray phosphate finish, at least in 67. I see many repro hold-offs and the cover cap is a gold cadmium color. Maybe that was later in 68-69 but this doesn't seem the case for '67. I have researched the CRG archives but can not find a definitive answer as to what the finish should be though I have seen another thread where another person with an early 68 Z had the same interior finish. Many say it was a bright zinc to gold finish. I'll be bringing pictures to shows in case the judging questions it.
  Any other 67 or early 68 owners see the same on your hold-offs? If you haven't opened yours up yet, you  may want to do it. It is a surprise of the amount of brown crud that develops inside though the outside looks clean.
Thanks to Muscle Car Research LLC for the fast delivery and excellent price!

Thank you,
Mike

[sah62]

You're welcome, Mike! With respect to reproducing the finish, take a look at this article on my site:

https://www.musclecarresearch.com/rust-removal

Products like Evapo-Rust seem to leave a grey phosphate-like coating on treated parts. I haven't tried soaking parts that aren't very rusty (like the fitting in your pics above), but it might be worth experimenting to see if you can reproduce the finish that way. If it doesn't work you can buy manganese phosphate concentrate from companies like Palmetto Enterprises:

http://www.palmettoenterprises.net/Palmetto_Enterprises/-Welcome-.html

[Mike S]

Hi Scott,

  I have the solutions for gray parkerizing. I soda blasted the part on the outside and it cleaned up really nice. I'll parkerize it to restore it to its original finish. The main body I may paint black or leave it and cover it with RPM. My guess is the cast parts may or may not have been painted. I wish I could look back 45 years to see for sure. So much for the repos as they can be misleading in what is supposed to be correct.

Thanks,
Mike

[NoYenko]

Mike, I too just received a seal kit from Scott @ Musclecar research. Took my early 1969 valve apart and found the same finish as your picture. No gold or yellow cad as on the reproduction pieces. George

[Mike S]

Hi George,

  Thanks for the input. That is good to know and I see it extends into 69!
Question,...how will you be finishing the outside main body...cast or black?

Thanks again,
Mike

[tmodel66]

Mike according to TPTB when I built my car natural cast was original but painted black is now acceptable. I also painted my master cylinder black which I was told is also acceptable.

[NoYenko]

Mike, the body of the valve I painted with cast look paint, the big plug I plated dark phosphate. The support bracket I hound a hint yellow cad under the bracket bolt so I replated yellow cad. Here is a not so great picture. George

[Mike S]

  Interesting to see your bracket also has a groove in it  like mine on both cars. This is absent in the repos. I also noticed your bolt is black compared to the repos zinc.
I removed the one on my survivor as well as examining the original one on the convertible I am restoring and they both are clearly black phosphate.
So much for the repos!
  I'll likely keep the body raw cast (it cleaned up great with glass beading) and coat with RPM to preserve it and gray phosphate the cap.
Compared to the repos, there's a lot of differences.

Thanks again for all the replies.

Mike