PRODUCT DETAILS
ACT HD Rigid Race Clutch Kits: HC5-HDR4 and HC5-HDR6
You've kept the SOHC engine and manual gearbox in your Civic, and now you're choosing a clutch for race use. ACT offers HC5 with either four or six ceramic pads, a rigid center and the H023 Heavy Duty pressure plate. Both kits are rated for 300 lb-ft at the crank. The difference is in the disc, not a higher torque limit for the six-pad version.
Ceramic friction with a rigid center
For this job ACT uses ceramic pads on a rigid disc, with a heat-treated chrome-moly hub. You're buying ceramic friction material for its heat tolerance under race use. The rigid center has no damper springs; it keeps the disc light for quick shifts, with less cushioning as the clutch engages.
That choice isn't free of compromises. ACT warns about increased gear rattle and possible spline wear, and describes engagement as aggressive. On a track build you may accept that behavior. On a car you drive to work, we'd think twice about giving up a smooth takeoff just to get the rating on this kit.
If smooth road use is the job, we'd start with an organic street disc. The HC5 ceramic kits are race-only parts. You can choose the pad layout, but you're not changing that basic character by choosing six pads.
H023 is ACT's Heavy Duty plate. Its stamped cover keeps the assembly rigid, and the diaphragm goes through four heat-treatment stages. ACT checks clamp load and balances each plate. Both kits have the light-to-moderate pedal feel ACT lists for this application. Your pedal may be manageable, but the disc will still take up sharply.
Four pads or six
If your engine is making more torque than the kit's rating, adding two pads isn't the answer. HC5-HDR4 and HC5-HDR6 are both rated at 300 lb-ft at the crank, not at the wheels. Choose capacity first, then decide which disc you'd want in that application.
Both discs are 212 mm, so the six-pad option doesn't give you a larger-diameter clutch. ACT lists the four-pad assembly at 9.7 lb and the six-pad assembly at 10.3 lb. Those numbers describe the clutch assembly; they aren't boxed shipping weights.
ACT describes its four-pad rigid discs as a good choice for smaller clutch sizes, with harsher engagement. The six-pad layout absorbs more heat. We'd base the choice on the response and heat absorption you're after, once you've confirmed the torque rating suits the engine. If what you actually want is a sprung hub, you'll need a different disc family. Both of these centers are rigid.
| Disc Pads | SKU | ACT Kit | Disc |
| 4 Pad | actHC5-HDR4 | HC5-HDR4 | 4212004 |
| 6 Pad | actHC5-HDR6 | HC5-HDR6 | 6212004 |
Specifications and kit contents
| Torque capacity | 300 lb-ft at the crankshaft, both options |
| Disc | 212 mm / 8.3 in, ceramic friction, rigid chrome-moly hub |
| Input shaft | 7/8 in diameter, 20 splines |
| Pressure plate | H023 Heavy Duty |
| Release bearing | RB820 |
| Pilot bearing | PB1002 |
| Alignment tool | AT20 |
| Flywheel | Not included |
| Intended use | Race only |
SOHC manual-transmission fitment
| Year | Make / Model | Application |
| 1992-1995 | Honda Civic | CX, DX, EX, LX, Si, VX; SOHC 1.5L / 1.6L |
| 1996-2000 | Honda Civic | SOHC 1.6L applications; excludes DOHC Si |
| 2001-2005 | Honda Civic | SOHC 1.7L applications; excludes DOHC Si |
| 1993-1997 | Honda del Sol | S and Si, SOHC 1.5L / 1.6L; excludes DOHC VTEC |
| 1997-2005 | Acura EL | Manual 1.6L / 1.7L applications |
Say you're ordering for a 1994 del Sol Si. With the original SOHC engine and manual gearbox, it's in the HC5 application. The B-series del Sol VTEC isn't. Don't let the Si name make the choice for you on a Civic, either: ACT's regional SOHC Si listings don't cover the US DOHC Si. Check the actual engine and gearbox on a swapped car. Automatics and CVTs aren't covered.
Before the gearbox goes back in
A part-number comparison can catch another ordering mistake. HC4 and HC5 use H023 and the same disc numbers, but they don't have the same release bearing. HC5 has RB820. For a stock SOHC 1998 Civic EX manual, choose the kit for that drivetrain instead of substituting a complete early Civic/CRX kit because the plate matches.
You'll need a suitable flywheel separately. If you're keeping the one from your car, check its surface before bolting on the new clutch, and follow its manufacturer's resurfacing limits. Check the input-shaft splines and the release fork while you have access, too. You'll still be relying on those parts once the gearbox goes back in.
AT20 comes in the box to help you center the disc. Keep ACT's instructions open for disc orientation and the assembly sequence. You'll need the fitting and tightening specifications for the parts you're using, too.
Read ACT's race-disc bedding instructions before you drive it. The 300-500 mile advice you may have seen is for ACT's organic street discs. It doesn't automatically apply to this ceramic disc, and ACT warns against overheating the friction surfaces during bedding.
ACT's limited warranty runs for 12 months, subject to its warranty terms. Keep your purchase receipt. Installation labor isn't covered. Both HC5 variants also have a California Proposition 65 warning.
SOHC D-series manual-transmission applications only: Civic 1992-2005, del Sol S/Si 1993-1997 and Acura EL 1997-2005. Excludes DOHC Civic Si, del Sol VTEC, automatic and CVT applications. ACT regional SOHC Si listings do not cover US DOHC Si models. Engine swaps require verification of actual engine, gearbox, input shaft and flywheel.
H023 pressure plate, selected 4212004 four-pad or 6212004 six-pad rigid ceramic disc, RB820 release bearing, PB1002 pilot bearing and AT20 alignment tool. Flywheel not included.