Eibach's 9310.140 is a set of four track-developed Drag-Launch springs for V8 Mustang coupes, designed to shift weight onto the drive wheels during a hard start. The manufacturer lists this kit for the 1979-1993 Mustang Coupe V8 (FOX), the 1994-2004 Mustang GT Coupe (SN95), and the 2003-2004 Mustang Mach I Coupe V8 (SN95), so confirm your exact year and trim before ordering. The manufacturer notes the springs were tested with factory dampers, which makes them a practical choice if you want to keep your stock shocks and struts. Stock springs are tuned for ride comfort rather than a repeatable launch, and this kit targets lower quarter-mile times and more consistent starts. Owners on user forums describe an airbag that goes into the right rear spring, which they say helps keep the car from twisting on launch.
Owners on user forums say the springs are streetable. One owner reports they lower the car very little and seem to have good manners on the road, so the kit suits a street/strip car better than a show build. Keep the shopping list tight: the manufacturer's listed 1/4-mile benefit has no confirmed time figure here, so treat the performance gain as a directional benefit and track-test your own car to measure it.
Front installation is the hardest part. Owners on user forums say the fronts sit a full coil taller than stock, and they generally use two spring compressors, a jack to raise the lower control arm, and a safety chain. The rear is easier: one owner describes jacking the rear control arm and unbolting it from the axle housing. Search terms worth targeting include 9310.140 drag launch springs, 1979-1993 Fox Mustang drag launch kit, SN95 Mustang drag launch springs, and Mach 1 quarter-mile springs.
The manufacturer lists three applications: the 1979-1993 Mustang Coupe V8 (FOX), the 1994-2004 Mustang GT Coupe (SN95), and the 2003-2004 Mach I Coupe V8. Confirm your year and body style against this list before ordering.
Owners on user forums describe an airbag that installs in the right rear spring to preload that side during a launch. Confirm the complete contents with the manufacturer before purchase.
The manufacturer states the kit was tested with factory dampers, so it is designed around stock shock and strut setups.
Owners on user forums rate this a moderate-to-advanced home install that needs a jack and jack stands, spring compressors, a pry bar, and a helper. One owner describes unbolting the front strut from the spindle to access the spring, while another removed the caliper, rotor, and strut before pulling the stock coil. Rear springs can be swapped by lowering the rear control arm, which some owners do without a spring compressor. Watch for two gotchas: some owners report needing to drill the spring perch to route the airbag line, depending on control arm design, and opinions differ on whether a coil must be cut to fit the fronts. Follow the manufacturer's install document for spring orientation and front/rear identification, and confirm the procedure before you start.
