C2 - F41 Option/Rear Spring Question

[Rory Riedy]

Is there any way of telling if my 1966 BB Roadster came with the F41 Heavy Duty Suspension Package?

I'm in the middle of a body off & am not sure exactly what I have. The front spring appears to be HD but I am not sure if they are orignial or not (no lables or markings). The rear spring is a standard 9 leaf 2 1/4", however someone added a 5/16" x 1 7/8" x 7 1/4" rough cut steel shim plate between the differential housing & the top leaf.

Any clue as to why the shim plate was added?

I have the rear spring apart & plan on restoring. Is it worth the effort? Does the addition of the shim plate indicate someone believed the rear spring was shot or was someone just trying to adjust the ride height?

I am kind of lost here, any help or opinions would be greatly appreciated.

As Always Thanks,

Triple R

[Jack H.]

Absent....

factory original documentation (statement from original owner, bill of sale, Etc.) there's no way to REALLY confirm a given car's original configuration once it's gone through multiple prior-owner hands....

Often, these classic cars were raced, wrecked, repaired with their configuration changed along the way based on prior owner wim & the availablity of whatever parts that could be gotten a hold of. About the best you can really do is INFER a given car's original configuration based on forensic inspection (does this/that affected component agree with the option being analyzed?).

But, in the end, that's all the analysis will yield--an educated opinion that the car had this or that option. You simply can't tell without the supporting factory paperwork (and sometimes that's questionable too) that items and related items weren't changed somewhere along the line in the car's prior life!

[Rick A.]

Re: C2 - F41 Option/Rear Spring Question

Rory,

not a 1966 owner, but I thought ALL midyears with heavy duty suspension had a 7-leaf rear spring

[John H.]

Re: C2 - F41 Option/Rear Spring Question

In '66, F-41 was only available with the L-72 engine, and included a 7-leaf rear spring (all leaves cambered - no flat three upper leaves like the base 9-leaf spring). An added leaf/plate at the top of the spring would raise the rear ride height by the thickness of the added part.

[Joe L.]

Re: C2 - F41 Option/Rear Spring Question

Rory-----

Are you sure that the rear spring is original? Original GM springs did not have the plate, but many GM and other SERVICE springs do have an added plate to make up for differences in spring leaf thicknesses.

As John mentioned, all springs used with F-40/F-41 suspension during the 63-72 period used 7 leafs in a non-progressive-rate configuration (all leaves arched in the free condition). All 1964-74 standard rear springs were 9 leaf, progressive rate springs (3 top leaves "flat" and lower 6 leaves arched in the free condition).

[Rory Riedy]

Re: C2 - F41 Option/Rear Spring Question

Joe & Others,

Thanks for the quick responses. This shim plate I refer to is by no means any thing that was part of a GM or service replacement. The shim plate has torch-cut edges & a torch-cut hole in the center, amaturish at best. Other than that I am pretty certain that the 9 leaf spring is an original, top 3 flat, bottom 6 arched. I just don't know if it was originally on this car because of the possible HD front springs.

If I were to guess, I would bet the car had original standard duty front & rear springs & that someone tried to beef up the suspension by changing out the front springs & then added this "scab spacer" to increase the the rear riding height.

What's your opinion?

How can I tell if the 9 leaf spring is still good & worth restoring?

Thanks,

Triple R