My next project is to fit coilovers to the front of my '85.
I need to be able to adjust the front of my car for street use and hillclimb and change spring rates if necessary.

Before I pulled the trigger on any units I did my research on CF and some other sites and learned a few things from the others that have gone before.

84 - 87's have a problem in narrow shock towers, later years have a wider tower.
problem overcome by either widening the tower by bending out with an adjustable wrench, or cutting off the tower and welding in a new one.
Vendors such as Vansteel offer bolt in C4 coilovers by hanging them upside down to help clear the narrow tower. They supply a custom top bracket.

next problem is lowering the front of the c4 results in running out of compression stroke on the shocker.
the front shockers are 10" compressed and 15" extended.
solution - use a 9" - 14" shock.

I have a friend who is a suspension guru (mainly in dirt track speedway) so I went and picked his brain.
He didnt like the idea of upside down shocks, unless they are specifically designed to run upside down, are gas charged and have reservoirs.
He did agree with running 9" - 14" stroke, and said to buy rebuildable and revalvable shocks.
I did get a big lecture about dynoing shocks etc.

As a result of my homework I then went about finding a shock, and that is not as easy at seems, taking into account my needs.
#1 - must be affordable, my budget doesnt extend to Penskes etc.
#2 - must be double adjustable alloy coilover.
#3 - must be able to operate at 11 1/2 " to 12 1/2 " shocker ride height
#4 - must be rebuildable.
#5 - must have stud top and T bar bottom fittings to suit C4.

Only 1 shock fits the bill, the Flaming River #FR70028 at $250 each.
I dont know much about this brand, except they are USA made and look very suspiciously like a QA1.
I also face extra costs being in Australia with dollar difference and shipping adding up.
So trigger is now pulled and the shocks have arrived from Summit.

 

First issue, these coil-over shocks do not come with a top spring mount !

I asked Flaming river about this before I bought them, couldnt get a straight answer, it would appear that the guy on live chat isnt allowed to go and open a box and look !

Not wanting this to become an issue, I ordered some angled QA1 top mounts with the shocks, these will give some clearance, so first issue avoided.

 

Flaming River buys them, mfgr'd to their specification from Vi-King shocks.

http://vi-king.com/

Should do a good job for you.
Will

 

Looks like you found more info than I did on how to coil over 84-87, so I'll subscribe.

 

Getting ready to do coil-overs on a 85 also, only seen one company that is doing it

http://emracingcorp.com/scripts/prod...?idproduct=292

be nice to have options, will be watching, hope I can find a good setup

 

thanks, I wasnt sure who made them, Im pretty well restricted to buying from Summit (due to range of brands and overseas shipping options) and they have them listed under UMI Performance, but nothing to suit c4.

 

I know that the coilover subject has a lot of interest, so I will post as i go along as it will hopefully help others looking at doing this.

 

I did look at the EM Racing set up, they arent adjustable which was a deal breaker for me.
I see that they use a thin body front shock (Im guessing 1.5") to get inside the shock tower. This will also make it harder to find springs in longer lengths, prob need to be custom made. They dont advertise what the spring rate is either ?

 

Will vi-king custom build a set for you if you call them?
I'm looking at doing fronts and rears on a 85

Springs and all "bolt on" or as close as possible

 

Next issue , the QA1 tops dont fit in the shocks, top hole too wide.

I found some suspension washers with 5/8 hole and rubbed them down on the belt sander to 43 mm outside diameter. You could probably just buy them if your in the States !

I got on the Flaming river live chat and asked, can you buy the spring caps to suit these shocks, and if so, what is the part number ?
His answer, YES.
if you put YES into part no. search it comes up 'not found'
If customer service is high on your list Flaming river would rate NO.

 

Those are prob meant for something else on top with a torrington bearing in-between, like in the foxbody coilover kits maybe http://www.uprproducts.com/mustang-p...ngs-black.html

edit: Also yah I agree when I saw the flaming river or another brand that re-labeled their shocks I though qa1 or vi-king, so you may want to just ask one of them directly your questions.

 

Forgot I saw those as well, but like you said non-adjustable and I didn't feel like seeing if they would break up the kit.

Still just like your doing I cold prob piece together something to work with my front drag shock for cheap.

FYI PAC racing is another place to look up suspension springs.

edit: FYI looks like all small body shocks cover over kits use a retaining clip, so I don't think you could coil over a drag shock.

 

its probably worth the call to viking to see what they can do.
I would even consider Vansteel, their set up uses QA1 shocks, just have to hope they dont leak if they are upside down !

 

I guess I should mention the next issue with coil-overs on the C4 - swaybar end links !

the coilover is fat and will hit the swaybar endlink,
the fix is rod end (heim) links or some people have bent the stock tower link to one side to clear,



Just another thing to buy and modify !!

 

Armed with the following information and the shocks I have been to visit guru Jim,

Wheel Rate
(you can get this info off the corvette suspension charts, http://www.corvetteactioncenter.com/...usp_chart.html)

this is applicable to a Z51 setup.
Front 163 lbs Rear 175 lbs

Motion Ratio
Front 0.759 (D1 = 11" D2 = 14.5")
Rear 1.00 (D1 = 18.25" D2 = 18.25")

Spring rate correction
Front 20 degrees = 0.88
Rear 10 degrees = 0.96

Unsprung weight
est 75 pounds per wheel

Weight ('85)
Front 1708 lbs
Rear 1453 lbs
(this weight includes driver in my car)

He did some other calculations including stuff I dont even understand fully (Hz rates etc)

End result is (ideal) spring rate around 550 lbs. This is taking into account 17 x 275 Nitto 01 street tyres on front and no aero.

He has recommended 595 lb springs for my application, taking into account the bumpy track that I usually run at combined with lowering the car some more (from where it is now) and not bottoming out.

 

One thing you need to keep in mind here; you cannot run shocks inverted.

If a shock is designed to run "upside down" (body up/shaft down), it must be installed that way. Same for a shock designed to run "rightside up" (body down/shaft up)....if you invert it, it will not function properly. Leakage has nothing to do with it.
A few shocks can be run either way without problems, by design, but they will inform you of this. Just pay attention.

 

Vi-King mfgrs smooth body shocks that are bolt on for C4s. I run them on my drag car... which is an 84.

I spoke at length with Vi-King reps at PRI this year and he wants to do a coil over kit for C4s but said that they haven't gotten a test car yet. I explained the difference between early and late shock towers to him.

Fact is that there's no way to use coil overs on an early C4 with out modifying the towers in some manner or using a Small Body coil over shock assy.

Also Van Steel has been substituting Vi-King shocks in some of their kits as of late.
Will

 

That is why I have been thinking very strongly about these
http://emracingcorp.com/scripts/prod...?idproduct=292

Actually I don't see much of a choice out there

Politically Incorrect and Proud of it

 

Here is a quote from a tech article,

Unless your shocks are specifically designed to be mounted upside down or designed to be mounted in either direction, please follow the rule stated above for dual shocks. As a rule, dual tube shocks should never be mounted upside down. Some people say that monotube or gas pressurize shocks can be mounted upside down, however in time they will develop and extra inch or more of piston travel that has little to no dampening effect whatsoever. Ultimately: don’t mount shocks upside down just because it looks cool. Sometimes a shock must be mounted upside down due to space limitations, or to protect the shock body, if this is the case, make sure you use a shock designed to be mounted upside down.

Most of your typical shocks designed for road based cars, such as the c4 (QA1, Flaming river etc) run twin tube, no gas shocks.

Generally shocks designed for upside down use are mono tubes and gas charged.

 

FWIW, Bilstein has a whole line of inverted shocks. I don't know if they can be set up as adjustable, but they can be custom valved. Seems like it would be possible to make an early C4 coilover kit based on those.