Correct coatings on reproduction trailing arm bolt and rear spring mount plate bolt

[Jerod M.]

On the right is a reproduction trailing arm bolt. On the left is a reproduction rear spring mount plate bolt.

I have never seen the "real things", but the coatings on the fasteners don't seem correct. Could someone please let me know what the proper coatings should be?

1971

[Joseph M.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Trailing arm bolts s/b cad/zinc. Leaf spring plate s/b black oxide.

[Jerod M.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Thanks, Joseph. It's hard to tell in the picture, but do your trailing arm bolts have a tapered tip on them?

[Alan S.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Hi Jerod,
In addition to Joseph's reply you may find the infrmation in the post by Joe L., that's part of this linked thread, useful.
I don't know if you've seen it or not.
Regards,
Alan

https://www.forums.ncrs.org/showthre...+bolt&uid=2482

[Joseph M.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

The trailing arm bolts have a tapered rounded end. They should also have a hole for a cotter pin. Not sure where you got the bolts you displayed, but Paragon or AMK typically have, but not always, reproduction hardware with the correct finish and headmarkings.

[Alan S.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Hi Jerod,
I looked at your picture again after your question and Joseph's reply.
I notice the spring mouting bolts have a longer part of the bolt threaded than the originals. I'm not sure if this matters or not. Might the threads damage the side of the longer/lower spring leaves?
Regards,
Alan

These are replated originals, (and 1 of Terry M's cotter pins), from my 71.

[Bill C.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

hey

just an FYI -- there is probably a good chance the repro bolts for the spring plate are going to be to long.

Compare the new ones to your old originals. If the new ones are longer - DO NOT USE them. Get your old ones replated.

Maybe they have gotten better with the bolt lengths now - but not sure.

Bill

[Jerod M.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

hey

just an FYI -- there is probably a good chance the repro bolts for the spring plate are going to be to long.

Compare the new ones to your old originals. If the new ones are longer - DO NOT USE them. Get your old ones replated.

Maybe they have gotten better with the bolt lengths now - but not sure.

Bill

Okay, I will check them. I only have two originals, so I was really hoping they were going to be correct.

[Jerod M.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

The trailing arm bolts have a tapered rounded end. They should also have a hole for a cotter pin. Not sure where you got the bolts you displayed, but Paragon or AMK typically have, but not always, reproduction hardware with the correct finish and headmarkings.

I bought them from Ecklers. (foul or okay vendor?) They look correct, but I'm not sure about head markings. The zinc is bright rather than grey and no spangle. Big issue?

[Jerod M.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Hi Jerod,
In addition to Joseph's reply you may find the infrmation in the post by Joe L., that's part of this linked thread, useful.
I don't know if you've seen it or not.
Regards,
Alan

https://www.forums.ncrs.org/showthre...+bolt&uid=2482

Thanks for this great link.
I see a theme...
Black Phosphate
Zinc
Plain

Looks like I need to order a black phosphate plating kit and a zinc plating kit. For the plain I assume I can degrease, wire wheel, and spray a light clear to prevent corrosion.

[Joe L.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Thanks for this great link.
I see a theme...
Black Phosphate
Zinc
Plain

Looks like I need to order a black phosphate plating kit and a zinc plating kit. For the plain I assume I can degrease, wire wheel, and spray a light clear to prevent corrosion.

Jerod-----

I wouldn't bother with re-plating. Paragon and their dealers have excellent reproductions of the trailing arm bolt and related parts as well as the spring retainer plate bolts. However, the trailing arm bolts you already have might be OK. I just can't see them well enough in your photo to say, for sure.

[Patrick H.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Thanks for this great link.
I see a theme...
Black Phosphate
Zinc
Plain

Looks like I need to order a black phosphate plating kit and a zinc plating kit. For the plain I assume I can degrease, wire wheel, and spray a light clear to prevent corrosion.

The trailing arm bolts you show are already zinc plated, which is correct. Zinc plating is shiny silver - just go check out the zinc stuff in the hardware store. Much of today's zinc is shinier than many years ago, but it's the same stuff.

FYI, to remove the zinc from the spring bolts you can strip them with muriatic acid. It will bubble as the hydrogen is released, so watch out for acid spatter.

Patrick

[Ronald L.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

Couple of things here...

Black oxide would not be a chassis finish as it has zero corrosion resistance. I see half way down we're talking of black phos which is the proper finish.

If you strip these bolts with acid...
Make sure you bake them to remove the hydrogen embrittlement, or you could have a catastrophic event.

Zinc today and yesterday....

Most of the fasteners back in this time period were just zinc, they had a corrosion requirement and the zinc coating had to be adequate to pass that spec. Later on yellow chromate or clear chromate were added as corrosion enhancers and those impart the blueish bright and or yellow look.

[Ronald L.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

If you plan to judge the car, you need to pay close attention to the head marks as the catalog stores just sell what ever and while you might get past a local show usually the national judges can know those differences.

[Joe L.]

Re: Correct coatings on reproduction trailing arm bolt and rear spring mount plate bo

If you plan to judge the car, you need to pay close attention to the head marks as the catalog stores just sell what ever and while you might get past a local show usually the national judges can know those differences.

Ron------


I seriously doubt that any judge will ever see the headmarkings on these trailing arm pivot bolts except, perhaps, those doing a Survivor judging.