Does anyone have suggestions for coil over shocks for an 89 C4 for drag racing use?

 

….. Don't ... unless you have to ! … if you have something other than stock suspension then go ahead … if stock , just replace all the trailing arm and strut rod bushings with poly and try to find a stiff rear spring … I get air under the fronts at launch that way …..

 

I'm assuming that I will have traction problems with the stock suspension. I in the process of building the car to 7-800+ rwhp.

 

….. At that power level , you should very strongly consider using a straight or live rear axle like a 9" Ford and ditch the stock rear stuff altogether …..

 

The form of spring you use (leaf vs coil) won't affect the traction. They literally both do exactly the same thing: hold the suspension off the bump stops and provide a linear(ish) spring rate. There is no magic to coil springs or coilover setups. If you stick with the stock IRS, you can get a 1984 Z51 rear spring, or look for the stiffest use VBP springs (they are now out of business). You could also probably benefit from the softest front spring (a base 1996 spring, I think). Then you can focus on finding good drag racing shocks, if any exist for a C4 IRS. Those really would help your rear traction at the strip.

ETA: The other interesting thing to play with would be increasing rear anti-squat by raising the frame-side mounting points for the trailing arms. This is not what you'd want for any sort of cornering, but for drag racing launches it would keep the rears tires from lifting into the wheel wells on launch (as will a stiff rear spring and maybe rear shocks with high compression rates). I don't know how high you can actually go with re-drilling the brackets or fabbing new ones before you run out of room or have some other physical limitation. But that would be an interesting experiment.

 

Are you going to run the Dana IRS after the engine is built ?
if so I would just worry about the shocks, look for a good double adjustable shock and you will be able to do some tuning in the rear end.
QA1, Viking and Strange all do shocks that will work in the c4 rear end. If you get a threaded shock you can upgrade later.

 

….. My heap only has around 600 at the flywheel and I'm rolling the dice with the original IRS … I haven't had any "real" failures yet but I have broken U-joint caps and crushed some U-joint needle bearings … I did break the nose off a Diff case once but that was by being stupid … currently using a Newman Car Creations diff housing with a newly machined / installed spool … no fancy shocks , though … mine are just some sporty Bilsteins … I weigh just under 3600# at the starting line so that doesn't help with longevity but check my avatar on M/T drag radials … I run M/T slicks now …..