Why Upgrade Your S13’s Clutch to a Clutch Masters FX350

The Nissan 240SX (S13) is a legend in the drift and street-performance world. Its lightweight chassis, rear-wheel-drive layout, and potent KA24DE or SR20DET engine make it a favorite for modifications. However, as you increase horsepower through forced induction, turbo swaps, or engine tuning, the factory clutch quickly becomes a weak point. Slipping, glazing, and premature wear are common symptoms of a stock clutch trying to hold 50%–100% more torque than it was designed for.

Enter the Clutch Masters FX350 – a heavy-duty, organic/fiber composite clutch designed for street-driven vehicles with moderate power upgrades. The FX350 offers a pedal feel close to stock while providing significantly higher torque capacity. It’s rated to hold up to 380 lb-ft of torque, making it an ideal match for SR20DET builds producing 300–400 whp, or for KA-T (turbo) setups pushing similar numbers. Compared to a full-race puck clutch, the FX350’s smooth engagement makes it daily-driver-friendly, reducing chatter and still allowing seamless gear changes.

In this expanded guide, we’ll walk through every step of installing the FX350 in your S13, from preparation to break-in. We’ll include torque specifications, alignment tips, and common pitfalls to avoid. Whether you’re a first-time DIYer or a seasoned mechanic, this article gives you the confidence to do the job right.

Tools and Materials – What You Need

Before lifting the car, gather everything. Missing a tool mid-job can add hours. Here’s a complete list:

  • Clutch Masters FX350 Clutch Kit – includes disc, pressure plate, release bearing (pilot bearing sold separately if needed).
  • Pilot bearing (if replacing – highly recommended).
  • Clutch alignment tool – usually included in the kit, but double-check.
  • Flywheel resurfacing or new flywheel – crucial for proper clutch bed-in (see Clutch Masters FX350 product page for flywheel specifications).
  • Socket set – metric: 10mm, 12mm, 14mm, 17mm, 19mm sockets, plus extensions.
  • Torque wrench (ft-lb and in-lb ranges).
  • Jack and jack stands (2-ton capacity minimum).
  • Brake cleaner and shop rags.
  • High-temp moly grease for splines and pivot points.
  • Transmission jack (or a strong floor jack with a helper).
  • Penetrating oil (WD-40 or PB Blaster) for rusted bolts.
  • Safety glasses and gloves.

Preparation – Getting Your S13 Ready

Work on a level concrete floor. Disconnect the negative battery terminal – this prevents accidental starter engagement. Jack up the front of the car and place jack stands under the frame rails or subframe. Remove both front wheels for better access. If you have a cat-back exhaust, you may need to unbolt the mid-pipe or hangers to lower the transmission – plan for that.

Important: Before removing the transmission, spray penetrating oil on the bellhousing-to-engine bolts and the driveshaft bolts. Let it soak for 15 minutes. This step alone prevents rounded hex heads and stripped bolts.

Drain the transmission fluid to avoid spills when the driveshaft is removed. S13 transmissions use GL-4 75W-90 gear oil. A drain plug wrench (usually 24mm or 10mm hex) will be needed. Also, if your power steering lines are near the bellhousing, tie them out of the way.

Removing the Old Clutch – Step by Step

With the car safely on stands and the battery disconnected, follow this sequence. Refer to the Nissan S13 service manual for exact bolt specs if needed.

Step 1: Remove Driveshaft

Mark the driveshaft-to-differential flange alignment with a paint pen. Unbolt the four 12mm bolts at the differential flange. Slide the driveshaft out of the transmission tail housing. Use a plug or a plastic bag to cover the tail housing – prevents fluid drips.

Step 2: Remove Starter Motor

Disconnect the starter wiring – two 10mm nuts on the solenoid. Then remove the two 14mm bolts holding the starter to the bellhousing. Pull the starter out and set it aside, supporting its weight.

Step 3: Remove Transmission Mount and Crossmember

Support the transmission with a jack. Remove the four 14mm bolts holding the crossmember to the chassis. Unbolt the rubber mount (17mm). Lower the transmission carefully – only a few inches. There will be a slight angle; this is normal.

Step 4: Disconnect Clutch Slave Cylinder and Hydraulic Line

Unbolt the two 12mm bolts securing the slave cylinder to the transmission. Do not disconnect the hydraulic line from the cylinder – just pull the cylinder off the bellhousing and hang it with a zip tie. This avoids bleeding the clutch later. The line is flexible enough to move.

Step 5: Remove Bellhousing Bolts

There are typically four 17mm bolts and one 19mm bolt (upper passenger side). Use a long extension from the top. For S13 with KA24DE, the top bellhousing bolt is tricky – it’s accessible near the intake plenum. A wobble extension helps. Remove all bolts and store them labeled.

Step 6: Separate Transmission from Engine

With a helper or a transmission jack, pull the transmission straight back. The input shaft must clear the pilot bearing and clutch disc. Wiggle gently if stuck. Do not pry against the bellhousing – it can crack. Once free, lower the transmission to the ground or workbench.

Step 7: Remove Old Clutch and Inspect Flywheel

Remove the six 10mm bolts holding the pressure plate to the flywheel. Loosen in a star pattern. Lift off the pressure plate and disc. Inspect the flywheel surface – it should be smooth, free of grooves and heat cracks. If the flywheel is glazed or warped, have it resurfaced (0.008–0.012 inches removal) or replace it. A new flywheel is recommended for the FX350 (see Z1 Motorsports - S13 flywheels).

Step 8: Clean and Prep

Thoroughly clean the flywheel face and ring gear area with brake cleaner. Wipe the inside of the bellhousing – oil residue can contaminate the new clutch. Also, clean the transmission input shaft splines – remove any old grease or rust using a wire brush.

Installing the Clutch Masters FX350 – The Right Way

Step 1: Install Pilot Bearing

If you have a new pilot bearing (roller or needle type), install it now. Use a bearing driver tool – never hammer directly on the outer race. The bearing must seat flush with the crank flange. A misaligned or worn pilot bearing causes transmission vibration and difficult gear engagement.

Step 2: Align the Clutch Disc

Place the FX350 clutch disc against the flywheel. The disc is typically marked “FLYWHEEL SIDE” – ensure correct orientation. Insert the alignment tool through the disc and into the pilot bearing. This centers the disc for transmission input shaft insertion.

Step 3: Attach Pressure Plate

Set the pressure plate over the disc. Hand-thread the six bolts. Torque in a cross pattern to 23–25 ft-lb (check kit instructions). Use a thread-locker (Loctite 242) on each bolt – some S13 pressure plate bolts have been known to loosen under high heat. After torquing, remove the alignment tool. Verify the disc is centered by turning the tool – it should rotate freely without binding.

Step 4: Grease Splines and Release Bearing

Apply a thin layer of high-temp moly grease to the input shaft splines – do not overgrease, or it can sling onto the clutch disc. Also grease the release bearing hub where it contacts the clutch fork. A new release bearing is included with the FX350 kit – install it on the fork before transmission reinstallation.

Reinstalling the Transmission – Patience Pays

The transmission weighs about 80 lbs – use a helper or a transmission jack. Have the clutch fork properly aligned with the release bearing. Slide the transmission forward – the input shaft must pass through the clutch disc splines. Gently rotate the output shaft to align splines if needed. Do not force – if it hangs, adjust the angle and try again. Once the bellhousing is flush against the engine block, hand-thread the bellhousing bolts.

Torque bellhousing bolts in a systematic order to 35–40 ft-lb for 17mm bolts, 40–45 ft-lb for the 19mm upper bolt. Reconnect the slave cylinder – torque its two bolts to 12 ft-lb. Install the transmission mount and crossmember – torque to 35 ft-lb at the chassis, 30 ft-lb at the mount.

Reinstall the starter motor (14mm bolts to 30 ft-lb). Reconnect starter wiring – do not overtighten the small nuts. Reinstall the driveshaft: clean the flange, apply thread-locker, torque the four bolts to 25 ft-lb. Fill transmission with fresh gear oil (approx 2.5 quarts).

Post-Installation Checks and Break-In

Lower the car, reconnect the battery, and start the engine with the transmission in neutral. Listen for rattling – a slight chatter is normal for a performance disc. Press the clutch pedal several times – it should feel firm but not heavy. Do not rev the engine while engaging gears yet.

Clutch Bleeding (If Needed)

If the clutch pedal feels soft or low, the system may need bleeding. Use a vacuum bleeder or two-person method. Bleed the slave cylinder with DOT3 or DOT4 fluid. Pump the pedal 10–15 times while holding a bleeder screw. Replace fluid every two years.

Break-In Procedure

For the FX350, follow a 500-mile break-in: avoid aggressive starts, full-throttle launches, or high-RPM shifts. Vary speed but do not lug the engine. Rev-match on downshifts. After 500 miles, you can perform a few moderate-WOT pulls (2nd to 3rd) to fully bed the clutch. The organic material will “burnish” and create a strong friction bond. A properly broken-in FX350 lasts 30,000–60,000 miles under normal street use.

Common Pitfalls and Troubleshooting

  • Transmission won’t mate: Check pilot bearing alignment; also ensure the clutch disc isn’t flipped. If the input shaft binds, remove transmission, verify the disc is centered, and reapply grease to splines.
  • Clutch dragging after install: Usually caused by a warped pressure plate or incorrect disc thickness. Torque all bolts evenly. Also check that the release bearing is fully seated on the fork.
  • Noisy release bearing: Ensure the bearing is properly greased and the fork pivot ball is not worn. S13 fork pivots are known to wear – consider replacing with an OEM pivot ball.
  • Hydraulic failure: If pedal sticks to floor, inspect the slave cylinder for leaks. S13 master cylinders also fail – upgrade to a 15/16” bore for improved feel.

Conclusion

Installing a Clutch Masters FX350 in your S13 is one of the most rewarding drivetrain upgrades. It gives you the torque capacity needed for a tuned KA24DE or SR20DET while retaining daily-drivability. By following this detailed guide – from cleaning the flywheel to properly torquing every bolt – you ensure a reliable, chatter-free installation. Remember: safety first, work methodically, and don’t skip the break-in. Your S13 will thank you with crisp shifts and solid grip under full throttle. For additional resources, check out Clutch Masters’ official site and the S13 community at Zilvia.net for real-world feedback and tuning tips.