C2 Leaf Spring Bolts

[Roger P.]

Hi Guys,
What is the correct color for the rear leaf spring bolts? I have seen both black and metalic. I am replacing my leaf spring bolts & cushions and want to make sure that the bolt color/finish is correct. Also, I ordered the longer bolts in order to adjust the ride height to factory specs. Since they are adjustable, they come with lock nuts (no cotter pins). Is that sufficient, or will the lock nuts loosen over time? Should I use Loctite on the bolts to ensure they don't slip?

Thank you,
Roger (50141)

[Ron G.]

Re: C2 Leaf Spring Bolts

Roger,

It is my opinion that the finish on the bolts is black oxide.

- Ron

[Michael G.]

Re: C2 Leaf Spring Bolts

Longer bolts will have the rear of car sitting lower. Spring perch bolts I believe are natural however didn't locate anything in the latest judging manual. Maybe others can add clarity.

[Joe L.]

Re: C2 Leaf Spring Bolts

Roger,

It is my opinion that the finish on the bolts is black oxide.

- Ron

Ron------

I don't think so. Black oxide was a finish that was extremely rare for Corvette fasteners. I believe these spring bolts were black phosphate.

For illustrative purposes, buy an ARP fastener. ARP fasteners are almost always finished in black oxide. I think you will see that there are few, if any, fasteners on a Corvette that appear anything like this.

Curiously, I think that the steering arm-to-spindle bolts for C3's might have been black oxide. These bolts that I've seen have a very smooth finish, more typical of black oxide than black phosphate.

[Ron G.]

Re: C2 Leaf Spring Bolts

Joe,

C3's I am confident were black oxide as many years ago when I first got into Corvettes I sat down with several local platers for just about everything on the car, and everyone said those particular bolts are black oxide. As for the C2's, my research was no where extensive and your'e probably correct.

- Ron

[Terry M.]

Re: C2 Leaf Spring Bolts

Ron------

I don't think so. Black oxide was a finish that was extremely rare for Corvette fasteners. I believe these spring bolts were black phosphate.

For illustrative purposes, buy an ARP fastener. ARP fasteners are almost always finished in black oxide. I think you will see that there are few, if any, fasteners on a Corvette that appear anything like this.

Curiously, I think that the steering arm-to-spindle bolts for C3's might have been black oxide. These bolts that I've seen have a very smooth finish, more typical of black oxide than black phosphate.

The phosphating process is often used in metalworking as an aid to lubrication. The phosphating opens up channels between the grains on the surface of the metal and those channels trap the lubricant during the forming operations. I think it is the Science Channel on cable television that has a program called "How it's Made" that in one segment shows the heading, threading and subsequent heat treating operation for making bolts. One can see that the coils of wire (it looks like it might be 1/2-inch or more in diameter) are phosphated before any operations begin. Sadly they don't show the phosphating operation, but the rest of the program might be of interest if you have the chance to see it. They also have a segment on making fuel tanks and one on shock absorbers. While the configurations are not of value to us, seeing the processes can be revealing. I suspect little beside automation has changed since our Corvettes were built.

[Paul J.]

Re: C2 Leaf Spring Bolts

I think it is the Science Channel on cable television that has a program called "How it's Made" that in one segment shows the heading, threading and subsequent heat treating operation for making bolts. One can see that the coils of wire (it looks like it might be 1/2-inch or more in diameter) are phosphated before any operations begin. Sadly they don't show the phosphating operation, but the rest of the program might be of interest if you have the chance to see it. They also have a segment on making fuel tanks and one on shock absorbers. While the configurations are not of value to us, seeing the processes can be revealing. I suspect little beside automation has changed since our Corvettes were built.

"How It's Made" is an excellent program. It provides insight to manufacturing processes which the average person does'nt get to see. Unfortunately, they try to have some diversity in every episode, so they leave out much of the actual processes due to time constraints. If this was'nt frustrating enough, the program is produced in Canada and concentrates on items which have more meaning there than in the southern U.S. (hockey masks, snowmobiles, hockey sticks, etc.) There is a similar program called "How Do They Do It", but I feel that it's not as good. Both of these programs are worth watching, especially if you've never seen the processes used to make machine parts like the ones in our Corvettes.

[Terry M.]

Re: C2 Leaf Spring Bolts

Aw Paul, come on. I thought the programs on snow shoes and canoes and kayaks were a hoot. They did a program on surf boards too. I guess it was PC to appease us south of the border folks.

[Michael G.]

Re: C2 Leaf Spring Bolts

The phosphating process is often used in metalworking as an aid to lubrication. The phosphating opens up channels between the grains on the surface of the metal and those channels trap the lubricant during the forming operations. I think it is the Science Channel on cable television that has a program called "How it's Made" that in one segment shows the heading, threading and subsequent heat treating operation for making bolts. One can see that the coils of wire (it looks like it might be 1/2-inch or more in diameter) are phosphated before any operations begin. Sadly they don't show the phosphating operation,

[Roger P.]

Re: C2 Leaf Spring Bolts

OK, so the bolts should be black. The longer bolts made by Paragon are "metallic" (perhaps cadmium plated?). I primed the bolts and sprayed them black as the gold metallic color obviously isn't correct. Will the lock nut they supply be sufficient, or should Loctite also be applied? The original bolt has a castle nut and cotter pin. I also wanted to know if the lock nuts on the longer bolts can be adjusted (tightened or loosened) when the car is back on the ground in order to "tweak" the ride height once the rear suspension settles.

Thanks,
Roger (50141)

[Shane G.]

Re: C2 Leaf Spring Bolts

The Nylalock nuts supplied with the adjustable bolts have worked just fine for me. While that set up will not pass for stock, it is very handy for adjusting ride height.

[Russ S.]

Re: C2 Leaf Spring Bolts

OK, so the bolts should be black. The longer bolts made by Paragon are "metallic" (perhaps cadmium plated?). I primed the bolts and sprayed them black as the gold metallic color obviously isn't correct. Will the lock nut they supply be sufficient, or should Loctite also be applied? The original bolt has a castle nut and cotter pin. I also wanted to know if the lock nuts on the longer bolts can be adjusted (tightened or loosened) when the car is back on the ground in order to "tweak" the ride height once the rear suspension settles.

Thanks,
Roger (50141)

The lock nuts they supply if they are nylock will be fine without lock tite. Yes you can re-adjust them after the car is on the ground but never run nylok nuts on or off with a impact gun as the speed of the turning nut could cause the nylon to heat up and decrease it's holding ability. Turn them slower by hand.

[Terry M.]

Re: C2 Leaf Spring Bolts

Thank you Mike. Your product knowledge is invaluable to us.

I should have realized the heating and forming operations would be the end of the initial phosphate process.

[Michael G.]

Re: C2 Leaf Spring Bolts

Terry, thanks for the kind words. Coming from someone with your experience depth of knowledge, the sentiment is greatly appreciated.

Those "How its made" segments are great, I watch them whenever I can, but sometimes they can't go into quite enough depth in the time allotted...

I see references to "black oxide" here a lot, so I thought I'd try to help clarify processes that I knew well in my many years on the GM finish committees.

[Ronald L.]

Re: C2 Leaf Spring Bolts

Any finish spec is applied after forming and heat treating.

I have hand fulls of both finishes, the black is not true black in color, more of a brown organo phos. The silver color ones which came later are finished with the 400 hour organo zinc. No cad.