1968 F 41 suspension

[Tom #44783]

I am rebuilding a 68 coupe with F 41 suspension. Would like to install new front springs and all 4 shocks. Any ideas where I could get these items or a close match. I hope to show this car at a NCRS show, so would like to stay as authentic as possible. Also judging book is unclear. Will I lose points if ball joints are bolted instead of rivited. Thanks in advance for your input.

Tom

[Joe L.]

Re: 1968 F 41 suspension

Tom------

F-41 rear shocks are still available from GM. However, the configuration of the current versions is not exactly the same as the originals.

For the most part, you'll need to find NOS parts for the restoration. I don't know of any reproductions of the parts you mentioned that would "fill the bill" for an absolutely correct restoration, assuming that's what you're after.

[John D.]

Re: 1968 F 41 suspension

Tom, If you don't use riveted ball joints you will definitely get dinged. Better purchase the Corvette Judging Reference Manual from NCRS. Look at the standard deduction guidelines for your shock problem. See the archives for the answer to your question on shocks. It's been covered extensively this past year and earlier. Good luck, John

[Mark #28455]

I am currently working on springs

The glitch is that there appear to have been 2 different springs available under the same part number! Yes, I already know what everyone will say - the GM specs were specific and the part MUST have met the specs!

My 1969 F41 cars both have original springs. I bought one of the last sets of F41 springs available through the GM parts system about 5 or 10 years ago hoping for a "NOS example" and although they had the same wire diameter and coil count, they were a shade short compared to the originals. When installed, the front of the car sat about 1/2" lower. I have already located a spring manufacturer who was willing to make a pilot run in the original wire alloy and diameter in the GM specs to both of the free heights, now I just want to install them to see how the ride height ends up!

I may be able to finally get around to this in the near future - Corvettes are just a hobby to me, my day job takes up a lot of my time.

Mark

[Joe L.]

Re: I am currently working on springs

Mark------

GM specifications for a particular part number can change. This happens with some regularity. I have seen cases in which a part changes drastically, but the part number does not change. In other cases, a tiny change in specs for a part results in the issuance of a completely new part number and specifications.

I show the free length specification for the GM #3832518 spring to be 10.84". However, some NOS SERVICE examples of this spring that I have measure 12" in free length. So, in this case, the SERVICE springs I have are actually longer than they are supposed to be.

[Mark #28455]

Re: I am currently working on springs

Thanks Joe!

Mine are all about 12" free length too, the original ones are about 1/4" longer than the later "NOS". I now have both lengths made up, just have to get out and test them. I can definitely agree with you that the 10.84" is nowhere near what I have seen (I also bought a few used original springs to compare with and they are about 12" too).

Mark

[Joe L.]

Re: I am currently working on springs

Mark-----

Very often, the GM methodolgy for determining dimensions of things for the specs is not the "intuitive methodolgy".

If Franz Estereicher happens to see this, maybe he can enlighten us on the methodology and/or the specs for the GM #3832518 springs.

[Terry F.]

Re: I am currently working on springs

Once I bought a set of springs from GM over the counter and installed them. They were suposed to be correct for my 427 68 corvette. I installed them and my car wouldn't even settle at all. The springs had the A-frames completely bottomed out. I took them back and installe my old ones. All was well again. Just thought I would add that. Take care, Terry

[Terry M.]

Re: I am currently working on springs

I had the same experience with GM front springs, and know several others who had the same experience. Some -- maybe many -- of the service replacements are too tall for some reason. I often see Corvettes with obvious height issues -- I think their other set of wheels are dubs.

[Mark #28455]

Re: I am currently working on springs

My service replacement F41 springs sat so low that a Pepsi bottle would have likely hit the oil pan! (it was really low) I dinged the pan the first day I tried to drive the car.
Mark

[Terry F.]

Re: I am currently working on springs

It is funny the number of things we have all probably repeated. One thing I can't stand though is a front end that is sagging. I hate it. It will take an other wise nice car and make it look tired. If you get the right tire and wheel well clearance, the car seems to get a balanced look. The same goes for a lot of vintage cars. So, I like a level car or a car with the front end just a tiny bit higher than the rear. Terry

[John H.]

Re: I am currently working on springs

The only meaningful engineering spec dimension for a coil spring is its height (length) at its design load, which is how they're designed, and how they're measured after they're bulldozed. Unfortunately, none of us have a test rig where you can drop a spring in, compress it, and read what the load is at design height. Free length is essentially meaningless, and hardly any of the replacement/aftermarket springs on the market are made anywhere near like the original variable-rate/progressive coil spacing design. Replacement springs are a crap-shoot, and "experimenting" to see if they'll produce the correct ride height is no fun at all.

[Terry F.]

Re: I am currently working on springs

It wouldn't be too hard to do. I personally would use a hydraulic press with a high pressure guage (after taking proper safety measures by chaining the sping to the press). I would compress the spring and make a two axis graph. Then I would go at it. Then, I would have everyone send me there known springs and start to make comparisons. I would approximate the hight of the spring under normal installation.

I will say this about my front springs on my 68. After I rebuilt the front end, the springs made it sit up rather nice. I suspect it will have a nice ride height now. So, I think it is really hard to tell if the spings are weak untill you rebuild the front end.

PS, Took me 4 hours to balance my check book this morning. What a mess! It is a good idea to look at it once in a while. Take care, Terry

[Mark #28455]

F41 spring doesn't have squared

Unlike a valve spring, the original F41 spring ends are just clipped off. The spring will not stand up on its own without trying to fall over. In order to test it, you would have to cut out the spring seats from 2 A arms to properly hold the spring. Having personally launched a few heavy parts using a hydraulic press in my younger (and stupider ) years, I would NEVER try to compress a suspension spring that way - you can do a lot of damage.

Mark

[John H.]

Re: F41 spring doesn't have squared

I've only seen three spring load/height testers - in the Suspension Lab at Chevrolet Engineering, one just like it at Chevrolet-Livonia Spring & Bumper, and Eaton Springs has one; very beefy, very safe too.