Hello All,

I’m new to this forum & new to C3 Corvettes. Like all mechanical things, they have charm and their challenges. Paul Dana was kind enough to recommend this forum.

I’ll provide a short history. I recently purchased a 1974 C3 with an aftermarket 502 big block. For the last 2 months I have been making multiple changes to make the engine run cooler. I may have finally found a solution. I made the following modifications: big block 2 row aluminum radiator, 16” electric fan, bigger alternator to run the fan sufficiently, Robert Shaw thermostat, Flow Kooler high flow water pump, spring in lower radiator hose, proper sealing around radiator core support, and wrapped headers.

I discovered Paul on eBay, and we have corresponded a bit. He has been very accommodating. I was going to correspond with him on this forum, but I see the rules require that I post first.

I have a rear suspension issue. Looking online, there is a great deal of conflicting information. I swapped the rear third member and had to purchase the more narrow rear spring. It has 9 leaves. That thing makes the car sit fairly high, and the drivability has diminished.

I’ve read everything from: let it settle over time, trim the spring ends & drill, remove the outer spring hardware to allow it to settle, remove a few leaves, cut the middle and re-weld, loosen the bolts and let it settle and re-tighten, install longer bolts, buy the aftermarket spring adjusters, install custom rear trailing arms, and replace with a shorter composite spring.

I believe this is the issue: When driving, the rear end is bouncing sideways on a somewhat small bump in the road. The rear stance/gap above the rear tires is too high. The new spring seems stiff. 9 leaves. The vehicle has wide back tires and rims, so longer bolts will cause rubbing on the tires. And while I could do it, I’m not real excited about cutting spring steel.

Given the myriad of advice out there, perhaps someone with experience in racing/lowering and stabilizing the rear of the vehicle could chime in with their experience.

Thanks in advance.

Regards

 

Welcome to the C3 Forum/Things Forum Members have advised me:
If you add a second fan (does not need to be as large as primary fan) the airflow thru the radiator will increase 30% or more.
ALSO...add a 5 second Delay relay to supply power to the smaller fan, This greatly reduces the strain on the alternator by staggering the startup of both fans.
That's alot of good spring advice you've collected/use the info that will help your problem.
It's easy to cut spring steel at the ends of the spring,,,use a right angle hand held power tool with a 4" by 1/32" or 1/16" thick cut-off disc attached to gain clearance at the rear tires.

Go to my thread and use the table of Contents to select the subject/pages for pictures of my modifications....clink on the link below,,,,,,
https://www.corvetteforum.com/forums...e-project.html

Ask if you have more questions.....

 

What shock absorbers do you have and how old?
What is the cold tire pressure?

 

For an unsettled rear end you need to look at rear bushing wear and wheel alignment. And of course the type and condition of your shocks.

As for your spring height issue, not sure how high, but it might be a few years before it settles to the factory specification of I think 27” (someone check me on that). I have a glass spring but it’s my understanding that new steel springs tend to be way high.

Easiest way to lower the car is longer spring bolts. I understand your wide tire issue, so what height are you shooting for? I guess a low arc fiberglass spring would be next easiest and then mods to your existing spring most challenging as you’re going to have to iterate a bit to get the ride height where you want it.

I would get the spring height to where you need to be then get it aligned. These cars get very skittish when the rear is out.

good luck!

 

When you mount a new rear spring you need to leave the 4 rear carrier bolts a little loose. Once you drop the car on the ground you can torque the bolts to the proper specs. If you torque the bolts with the car up in the air the rear end will sit higher than it is supposed to

 

Thanks for all of the responses. It is a new, rear, steel spring. I’m guessing that it will not relax a bit based on your observations for quite a while. I did lower the vehicle then torque the bolts - no difference. It sounds like I may be left with acquiring a composite spring. I see where some vendors offer them in shorter lengths.

Regarding height - after install it’s sitting somewhere around 31 inches which I understand is too high. After the install I noticed the increased gap over the wheel, the higher rear height, and the tendency to shift sideways on rather routine bumps while driving.

Any thoughts on rear alignment. My inquiry being - can any old alignment shop get this right, or will I need a specialist. Thanks again.

 

good point and you can also break the mounting ears the bolts go through

 

Welcome to the Forum!

Although it means buying the correct part after buying the wrong part, I'd highly recommend buying a low-arch composite spring from VanSteel. They are available cut down, if you need that. My VB&P spring (VanSteel now owns the molds) was cut down one inch.

If you want to read a story where an OP (original poster) takes a meandering journey to the correct solution, read this thread.

https://www.corvetteforum.com/forums...igh-still.html