Bolts for Rear Leaf Spring

[Steven A.]

I'm in the process of replacing a fibreglass rear spring with a steel nine-leaf spring on my 66 small block. The fibreglass spring was one of those VBP "dual mount" jobs which did not use the retaining plate bolted to the bottom of the differential. So I bought a new plate and bolts from Corvette Central to use to mount the new spring. Unfortunately the bolts that were supplied were much too long, especially for the front two holes.

I know I've seen this question come up in the archieves, but I was wondering if anyone knows the correct length for these bolts (mine are approximately 4 inches)? Also, is there a better source for these bolts or are all these parts suppliers selling the same poorly fitting parts?? P.S. I won't even get into the topic of how incorrect the spring itself is, I just hope it's functional.

Thanks in advance.

[Steve Wallach]

Re: Bolts for Rear Leaf Spring

East Coast Corvettes - call Steve Hack
513-553-2080 Tell him Steve from Chula Vista told you
to call him, he'll fix you up!

Good Luck,

Steve

[Gary B.]

CC repro Rear Leaf Spring

Steven,

Did you get the repro spring from Corvette Central as well? If so, let us know how it works out. I've been recommending the repro from Eaton Detroit Spring as people report good luck with that spring in terms of ride height. I'm interested in knowing if the CC spring also results in the correct ride height.

Gary

[William V.]

Re: CC repro Rear Leaf Spring

Steven

There are two bolt sizes available for (63-79)
For the HD 7 leaf spring, the bolt is 9/16-12x (3-5/16) long.
For the standard 9 leaf spring, the bolt is 9/16-12x (3-9/16) long.

BV

[Steven A.]

Re: CC repro Rear Leaf Spring

Will do. The spring is made by Triangle Spring which looks like a reputable outfit (based on looking at their website). I always thought the top two leaves on these springs were supposed to have no arch to them. This is clearly how CC depicts it in their catalog and web site. The spring I got has all leaves arched. I'm sure it differs from the original in many less obvious ways also. My car is not flight judging material anyway, so I'm not too worried about this, but I do hope the ride height and feel are within tolerable limits. I just wish the suppliers would be up front about what they're selling. Caveat emptor certainly rules.

[Gary B.]

Re: CC repro Rear Leaf Spring

Steven,

The original 9-leaf spring for '66 was a two-stage spring, with the top 3 leaves straight. Triange Spring is a long-time spring manufacture. So is Eaton Detroit Spring. Eaton can supply the two-stage version. I don't know if Triangle offers that version.

Gary

[Alan Drake]

Re: CC repro Rear Leaf Spring

Steve,
If you do not care about the spring for judging then consider the fiber glass style replacement spring. Weight is less and can get the variable spring rate that makes you happy.
If concerned with look, then get right one now - just spend money once.
Just a comment not being critical.
Alan

[Roy B.]

Re: Bolts for Rear Leaf Spring

Corvette stop in northern Ca. is great and honest I got mine there!

[Joe L.]

Re: Bolts for Rear Leaf Spring

Steve------

All 1963-77 Corvettes originally used spring retainer bolt GM #3833486. This bolt was a 9/16-12 bolt of 3-7/32" long. It was a special GM 280M (SAE Grade 5)bolt in that it had a non-standard shank-to-thread length. Since the shank of the bolt "aligns and locates" the spring, in this configuration, a minimum of threads were in contact with the spring.

The GM #3833486 bolt was GM -discontinued many years ago and replaced by GM #9428598. This bolt is a GM 300M bolt (SAE Grade8) more-or-less standard shank-to-thread configuration. It has a total length of 3-3/4" and a thread length of 1-3/8". Unfortunately, it's been discontinued, too.

I don't understand how a bolt that is about 1/2" longer than the original was used as a replacement, especially in this situation in which bolt length is somewhat critical. However, I can tell you that either of these bolts will work just fine with a spring of ORIGINAL THICKNESS.

[Joe L.]

Addendum

Just so there is no confusion since I used the term "bolt" instead of "bolts", I AM talking about the spring retainer bolts of which 4 are used per car. I am NOT refering to the spring CENTER bolt which is a 5/16", special head bolt.

[John L.]

Re: Bolts for Rear Leaf Spring

Steve & Joe, When I changed out my spring on my 79 I installed new Grade 8 Bolts of the correct lenght (as per what Joe mentions) I have had no problems with them so far. I got these from a local bolt jobber, I'm sure I paid less than $10.00 for all 4. Since Joe mentions that original GM bolts were grade 5, I feel comfortable with my choice. John

[Steven A.]

Re: Bolts for Rear Leaf Spring

Steve: Thanks. I spoke with Steve Hack today and I think he has what I need.