C2 Replacement Shock Length

[Jeff B.]

I'm just finishing the rear suspension on my 1964 restoration and I'm using the AC Delco 530-4 shocks (GM# 88945172). The car did not still have the original shocks so I have nothing to compare to but the new shocks seem a bit long and it seems like they should limit the travel a bit more. I have not put the links in the rear spring yet but it looks like it's going to pull down far enough to twist lower struts on their bushings a bit at the center bracket. Are these the correct shocks? Is this just how it's designed?

[Joe R.]

Re: C2 Replacement Shock Length

Delco 530-4 is the correct shock for 63-82.

Looks good to me and I've sold several. No returns as of now.

JR

[Joe L.]

Re: C2 Replacement Shock Length

I'm just finishing the rear suspension on my 1964 restoration and I'm using the AC Delco 530-4 shocks (GM# 88945172). The car did not still have the original shocks so I have nothing to compare to but the new shocks seem a bit long and it seems like they should limit the travel a bit more. I have not put the links in the rear spring yet but it looks like it's going to pull down far enough to twist lower struts on their bushings a bit at the center bracket. Are these the correct shocks? Is this just how it's designed?

Jeff-----


I agree with Joe. You have the correct shocks. By now, a LOT of these have been installed on Corvettes and I've never heard of a problem.

There are some incorrect parts in your installation, though. I assume you used the lower hardware that came with the shocks. This is 100% functional, but not correct. The lower washer should be a CUPPED shape washer with a natural finish and the cup facing OUTWARD. The lock washer should be a PLAIN finish. The nut should be a thick nut with a phosphate finish.

Also, the upper shock bolt should be black phosphate and not zinc plated. The nut, which is of course unseen in your photo, should a a thin jamb nut. My recollection is that it was zinc plated, but I'm not sure about that.

[Ridge K.]

Re: C2 Replacement Shock Length

Jeff-----


I agree with Joe. You have the correct shocks. By now, a LOT of these have been installed on Corvettes and I've never heard of a problem.

There are some incorrect parts in your installation, though. I assume you used the lower hardware that came with the shocks. This is 100% functional, but not correct. The lower washer should be a CUPPED shape washer with a natural finish and the cup facing OUTWARD. The lock washer should be a PLAIN finish. The nut should be a thick nut with a phosphate finish.

Also, the upper shock bolt should be black phosphate and not zinc plated. The nut, which is of course unseen in your photo, should a a thin jamb nut. My recollection is that it was zinc plated, but I'm not sure about that.

Once again, I agree with both Joe Ray, and Joe Lucia.
Here is a pic of the original shock for my "barn find", 46,000 mile 1967 convertible. Notice the lower CUPPED shaped washer, that although showing light surface rust on my midwestern car, one can tell it was originally natural finish. Joe L. is also correct on the lock washer. I'll take his word on the phosphate finish on the nut.
It measures 14 and 1/2 inches fully extended. I have compared it to currently manufactured shocks, and it is virtually identical, except for those key stamped dates, and manufacturer's name.

Hope this helps, Ridge.

[Jeff B.]

Re: C2 Replacement Shock Length

Thanks for the heads-up.

I do have the cupped washer facing outward and the double length nuts with a locknut but they are from Dr. Rebuild and came plated. Should I blast of the plating?

I have the original correct upper bolts with thin nuts but I had them cabmium plated (I was sure that's what the TIM stated but I must have got confused). Maybe I worked too late that night. While were on the subject I'm trying to verify the shape of the french locks on the half-shaft flange. I chose the ones with more of a rounded shape but several companies are selling thinner ones with straight edges as correct for the 1964.

No one will do black phospate. Will some flat black paint over the cadmium pass? If not then I guess it's black zinc.

[Ridge K.]

Re: C2 Replacement Shock Length

Thanks for the heads-up.

I do have the cupped washer facing outward and the double length nuts with a locknut but they are from Dr. Rebuild and came plated. Should I blast of the plating?

I have the original correct upper bolts with thin nuts but I had them cabmium plated (I was sure that's what the TIM stated but I must have got confused). Maybe I worked too late that night. While were on the subject I'm trying to verify the shape of the french locks on the half-shaft flange. I chose the ones with more of a rounded shape but several companies are selling thinner ones with straight edges as correct for the 1964.

No one will do black phospate. Will some flat black paint over the cadmium pass? If not then I guess it's black zinc.

Jeff, take a look at this discussion from two years ago, on this forum.
I know that fellow member Grant Wong is very knowledgable on black coatings.
Maybe others can jump in.
Ridge

https://www.forums.ncrs.org/showthread.php?t=45198&highlight=grant+wong+black+oxide

[Joe L.]

Re: C2 Replacement Shock Length

Thanks for the heads-up.

I do have the cupped washer facing outward and the double length nuts with a locknut but they are from Dr. Rebuild and came plated. Should I blast of the plating?

I have the original correct upper bolts with thin nuts but I had them cabmium plated (I was sure that's what the TIM stated but I must have got confused). Maybe I worked too late that night. While were on the subject I'm trying to verify the shape of the french locks on the half-shaft flange. I chose the ones with more of a rounded shape but several companies are selling thinner ones with straight edges as correct for the 1964.

No one will do black phospate. Will some flat black paint over the cadmium pass? If not then I guess it's black zinc.

Jeff-----


OK, I couldn't see the cupped washer in your photo; it looked like a flat washer to me.

As far as the nut goes, I don't know where you'd get those of original finish and configuration today. I think I'd be very reluctant to have these re-electro-finished. These are grade 8 nuts and any sort of RE-electro-finishing might compromise the strength. This is important because these are SAFETY-related. You could remove the plating by bead blasting and let the nuts rust. That's probably how most judges are used to seeing these anyway. Also, keep in mind that while I pointed out the finish was incorrect, that does not mean that I was recommending you change them. If it were me, I'd use them as-is.

With respect to the upper rear shock bolt, I've never seen one of these zinc plated. Perhaps some were, though. These were a grade 8 fastener (6 lines on the head). During the 60's and 70's it was unusual to find zinc plated, grade 8 fasteners on GM vehicles. Most of these grade fasteners were black-phosphate or black oxide finished. There were some exceptions, but they're few and far between. The 62-68 small block cranskshaft snout bolt was one exception I can think of off-hand, though.

[Patrick H.]

Re: C2 Replacement Shock Length

Jeff, take a look at this discussion from two years ago, on this forum.
I know that fellow member Grant Wong is very knowledgeable on black coatings.
Maybe others can jump in.
Ridge

It's very easy to do black phosphate at home.

If you want, Google "parkerizing" or "manganese phosphate."
Usually, places that sell the chemicals for use on firearms are great sources (Calvan is one). Manganese phosphate is black, zinc phosphate is a gray/dark gray.
I've been doing it for years without difficulty but have yet to try the zinc. It's coming soon.

Recently I've done several batches on the stove in the kitchen using a Teflon coated pan. I'm looking for a stainless pan now to see if it works a tad better. Either way, I can do a small batch in 15 minutes or so. You can do larger batches in a crock pot.

Patrick