Midyear rear spring trivia

[Tracy C.]

I've recently restored a 63 and a 65 rear spring and have learned a couple of things I thought I would share. Most may know the 63 rear spring is a single stage design and all 9 leaves are arched, but did you know the arch is not quite as pronounced on the 63 design? While I had these apart, I measured the arch of each of the first 6 leafs and got these results.

............63 spring........65 spring
leaf 1......8 5/8".............9 3/4"
leaf 2......7 3/4".............8 3/8"
leaf 3......6 3/8".............7 1/8"
leaf 4......4 7/8".............5 3/4"
leaf 5......3 3/4".............4 5/8"
leaf 6......3 0/0".............3 3/8"

The arch was measured on the bench with both ends butted to a straight edge. The distance measurement is from the straight edge to the inside surface of the center of the spring.

This pic shows a leaf by leaf comparison. the spring on the top is the 65 spring leaf in all cases. These are both low mileage takeoffs, so I'm confident the 63 is not just worn out. This may be common knowledge to some, but I learned something.



I also found some pretty compelling evidence that both sides of the 65 spring leaves were painted. This pic shows the compression (upper) side. I've always read that only the tension (lower) side of the leaf was painted.

[Wayne M.]

Re: Midyear rear spring trivia

Good info, Tracy -- here's a couple of pics I posted on subject of that IONOKLAD coating a few years ago. These are from my early '65. I believe back then we might have mentioned the possibility that what we see on the top center is "bleed-through" from excess applied to the bottom, when the "sandwich" of springs and liners was squeezed together.

Second pic is (I think) a few spring bottoms besides original shocks off same early '65 car, to show slight difference in color.

[Steve L.]

Re: Midyear rear spring trivia

Tracey,
While you have the spring apart, can you do a quick force measurement as per the attached pictures. This doesn't take very long to do. Your springs look in excellent shape. The force measurements would help others determine if their springs are still usable.

Also note that if you arrange the 6 springs in a circle you can get the overall spring diameter as shown in the attached picture. You can quickly see if any curves are flattened.

[Tracy C.]

Re: Midyear rear spring trivia

Steve,

I did the force measurements on both springs and posted into the other thread we had going a month or so back... This way the all numbers would appear in the same thread.

https://www.forums.ncrs.org/showthread.php?t=79623&uid=5869

tc

[Larry M.]

Re: Midyear rear spring trivia

When I rebuilt my 1967 rear spring (9 leaf) six months ago, the zinc coating was on BOTH sides of most or all of the leaves. The spring is original GM.

The lower side coverage was more uniform and complete, whereas the upper side was very mottled.

Both sides were cleaned/stripped using a 5 inch grinder with a scotch-bright stripping pad and then a wire wheel. They were then lightly blasted as needed (some areas on each spring needed additional help). I then sprayed a 95+ percent zinc "cold galvanizing" compound on each leaf. This spray has an epoxy binder, and holds up well in the chemical plants where we use it. And the color match to the OEM color is also very good. KRYLON Industrial Sprayon "Zinc Rich Cold Galvanizing Compound" #S00740.

Time will tell how well it works, but so far so good. I haven't found/seen anything better on the market to use.

Larry

[Timothy B.]

Re: Midyear rear spring trivia

I can't stand rust so it's a no brainer for me about painting both sides.

[Tracy C.]

Re: Midyear rear spring trivia

I can't stand rust so it's a no brainer for me about painting both sides.

Tim, there was no evidence of paint on the 63 spring, but l feel the same as you. The 63/4 says the springs should be painted so I did. Frequently we are deducted for "preservation" efforts on natural parts. In this case the JG provides a pass, so I jumped on it like a chicken on a Junebug.

I sprayed PPG DP50 grey epoxy primer followed by a zinc rich top coat like Larry used. I haven't top coated the 65 spring yet and you can see a slight color difference in the picture.

tc

[Domenic T.]

Re: Midyear rear spring trivia

I can't stand corrosion either so I powder coated my springs and they look great. I'm sure they won't judge well but I am sure they will look good for years.

DOM

[Timothy B.]

Re: Midyear rear spring trivia

When I did my 63 and 67 springs I glassbeaded then used a roller for the grey paint that came with the kit from Quanta. I believe at that time the kit was something like $65 but not 100% sure on that. Kit also included the liners and a centerbolt.

Make sure you grind the top of that center bolt before tightening to the rear..

[Domenic T.]

Re: Midyear rear spring trivia

Well Tim,
Funny, I have a 63 and 67 also, both coupes. My old bolt was in great shape so I parkerized it and used it over. I have not started on the 63 springs yet. I am waiting to get more room in the shop and the body back on my 67.

DOM

[Frederick W.]

Re: Midyear rear spring trivia

[QUOTE=Make sure you grind the top of that center bolt before tightening to the rear..[/QUOTE]

What do you mean by this?

Fred

[Tracy C.]

Re: Midyear rear spring trivia

What do you mean by this?

Fred

The head on some of the reproduction bolts that hold the spring together is too tall. A person needs to check the fit of the bolt head to the hole in the diff casting and grind it down if need be.

tc

[John H.]

Re: Midyear rear spring trivia

What do you mean by this?

Fred

Fred -

The thickness of the head on the replacement spring center bolt is taller than the original bolt, and it can bottom out in the hole in the rear cover casting before the top of the spring seats against the casting, which can crack or puncture the diff cover. The head of that bolt may need to be ground down to ensure that it doesn't bottom out before the spring does.

[Frederick W.]

Re: Midyear rear spring trivia

The head on some of the reproduction bolts that hold the spring together is too tall. A person needs to check the fit of the bolt head to the hole in the diff casting and grind it down if need be.

tc

Hmm
the wonders of aftermarket parts