Hi guys, yet another newb question here on suspensions to go along with all the others on the forum - I've had a look at the other posts but am not sure on a few things.

I recently bought a '68 with a 427; it's had the suspension re-done during the restoration but I'm not sure exactly what was installed. Not having any other reference point I'd have to say it handles OK for being pretty much stock (P215/70R15 tires, stock front sway bar, no rear sway bar, shocks look OEM), but the stance is just all wrong, being too high in the back and too low in the front.

When restored, a rear composite monospring was installed with long bolts, but I'm not sure of the spring rate. The front coils also appear new as they're nicely powder coated, but I don't know the spring rate on them either. So, given all that lack of information, any suggestions on how to get it to sit right?

I'm wondering about swapping out to OEM-style BB springs on the front to just raise it up, as that'd perhaps be the easiest fix?

Also, I'm considering putting Bilstein shocks on all four corners - any ride height impact with them?

And finally, as there's no rear swaybar I'm looking at installing an OEM-style bar there - any comments on that?

Thanks in advance for any help you can give me. I've attached a few pics of the car, label on the rear monospring if anyone recognizes that, as well as the front coils though I doubt that'll shed much light on anything.

 

1) When compared with modern offerings, ancient tire technology somewhat compromises handling limitations.

2) Don't have access just now to '68 BB ride height specs, but agree yours are obviously out of spec. The replacement rear leaf is most likely over-arched, which is apparently a somewhat common problem in the aftermarket. Installing a properly arched one should address the tail-high attitude without necessitating still longer bolts.

3) Suggest addressing the rear first, and then measuring your "Z" and "D" heights (illustrated below), and comparing that to either '68 specs and/or against Chevy Power Book recommendations* before deciding what to do up front, if anything.

4) Altering spring rates (or how much bar) is on one end of the car without also making the appropriate/offsetting change at the other WILL necessarily alter its understeer/oversteer balance. So, change these items without sufficient forethought at your own risk.

5) Installing a set of Bilsteins is among the best improvements many a C3 owner will ever make. There are reports of slightly increased ride heights, but not likely by enough to help in your case.

6) See # 4. Also, it is entirely possible to balance a C3 without a rear bar, so long as sufficient rear spring rate is practical/tolerable.



* http://www.corvettefaq.com/c3/ChevyPower.pdf

Hope that helps.


TSW

Oh, and welcome to the CF!

 

I agree with "Skunk Works".....get the rear end down where it should be, and the front may not look all that extreme.

 

Thanks for the quick feedback guys!

 

How much thread is left on your rear spring bolts at the ends. Loosen the nut will let the back sit lower


Loosen this nut

 

I am in the same boat your in, my 68 sits too high in the back. Even with a new set of Bilstiens all around. I put a composite spring in and the ride height got worse. Tried longer bolts, but it was maxed out and still too high. I got the spring from a local Vette parts boneyard type of place who let me return it and try other ones. The one that worked best ride height wise was from an 81 for some reason. Its not right and works OK for now, but next years project is a Vansteel Coilover kit in the rear where you can adjust the height.

 

I want to got to a monoleaf in the front so I can adjust all 4 corners. I love the ride I have no though

 

Rescue Rogers, that nut is at it's max position that'll still allow the cotter key to be installed - so no room for more adjustment, unfortunately.

Does anyone recognize the label on the monospring? I'm pretty sure it's the one on page 208 of the Eckler C3 Catalog (upper right-hand corner) but they weren't able to help me with a spring rate when I called. There are three possible options, 315, 340 and 355, but I'm not sure which one I've got. I'm guessing maybe it's the 315 and I've already got the long bolts - would a higher spring rate mean less bow (lower ride)?

 

its a trw spring part number 602-101, they punch out the number with a hole to indicate which of the three springs it is.
http://content.mamotorworks.com/pdf/trw%20spring.pdf

can you post pictures of the rear spring bolts and the mounting of the spring to the differential, and the half shafts in relation to the ground.
what size are the rear tires?

 

MelWff, thanks for that - so confirmed it's the 315 monospring. Rear tires are P215/70-R15. Requested pictures are attached.

 

Those repro TRW rear springs are notorious for jacking the rear ride height up too tall.

Your gonna need some 10' long bolts to get the ride height down where it belongs.
Will

 

I agree with the other posters who suggest to correct your rear height first and see how it affects the overall stance. Your front height does not look much different front the height on my 68 convert, judging by the spacing at the top of the front tire.

 

Thanks rklessdriver... With the current 8" bolts I have 5" of ground clearance from the leading edge of the bolt, same as the lowest point on my tailpipe, so I think extending another 2" would probably put me where I need to be in terms of ride height but seems too close to the ground for the bolts themselves? Has anybody done this? I have done some digging and find 10" bolts for C4 suspensions, but only up to 8" for the C3's?

 

Vbandp.com has Mono Leaf Installation Instructions, maybe worth reading. It also states the Vehicle Is Height Adjustable. Could be the shop that originally did the installation missed a step.
Good Luck