ACT 1971 Pontiac Firebird HD/Perf Street Sprung Clutch Kit

Restoring or hot-rodding a 1971-1974 Pontiac Firebird with a manual gearbox and a tired clutch? The ACT GM8-HDSS kit replaces the pressure plate, disc and pilot bearing with a Heavy Duty diaphragm plate and an organic street disc sized at 10.5 inches. ACT rates it at 629 ft-lb at the crank, 32 percent over the original clutch, so it handles a freshened V8 with a cam, intake and headers while still driving like a street car.

What the GM8-HDSS clutch kit does in a Firebird

Early second-generation Firebirds used a mechanical clutch linkage: the pedal works a rod and a pivoting cross-shaft, often called the Z-bar, that pushes a fork inside the bellhousing. The fork moves the release bearing against the pressure plate fingers. ACT's Heavy Duty pressure plate uses its own diaphragm design, which ACT says raises clamp load, reduces deflection and extends clutch life. The 3000903 disc uses premium organic lining with high copper content, a steel backing for burst strength, a sprung hub to soak up driveline shock and reduced marcel for quicker shifts. ACT describes the feel as light to moderate pedal effort with smooth, positive engagement.

ACT expects Heavy Duty plates to raise pedal effort by roughly 15 to 40 percent depending on the car, so a worn linkage will be more noticeable after the swap. Plan to check the bushings while the car is apart.

Symptoms that mean the clutch is due

• RPM flares in second or third gear under full throttle without the car pulling harder
• A shudder from a stop, often worse with old engine or transmission mounts
• A burnt smell after a few hard launches
• The clutch engaging right at the top of the pedal, or not releasing fully so gears grind
• A squeal or whir with the pedal pressed, which is usually the release bearing

How to confirm it before you buy

On these cars, rule out the linkage first. Worn Z-bar ball studs and bushings, a bent fork, a misadjusted pushrod or broken frame mount can all keep the clutch from fully engaging or releasing and feel exactly like a worn disc. Set the pedal free play to the factory spec, then do a slip test in third gear at low RPM and full throttle. If RPM climbs while speed lags with the linkage correct, the disc is done. Our clutch slipping guide and clutch chatter guide cover the checks, and the slipping diagnosis guide helps separate clutch slip from other driveline faults.

Fitment

Our listing is titled for the 1971 Firebird. ACT's fitment table for GM8-HDSS covers the 1971, 1972, 1973 and 1974 Pontiac Firebird Base with the 5.7L V8, and ACT's application note calls for a 10.5 inch clutch with a three-speed manual. The disc fits a 1-1/8 inch input shaft. Forty-plus years on, many of these cars have had engine, flywheel or gearbox swaps, so measure what is in your car: confirm a 10.5 inch flywheel friction face, the pressure plate bolt pattern and the input shaft spline before ordering. A car converted to an 11 inch clutch needs a different kit. If in doubt, send us the year, VIN and what you found. More clutch kits are in our clutch and rebuild kit collection.

Install notes

• The kit contains the GM012 Heavy Duty pressure plate, the 3000903 Performance Street sprung disc, the ATGM026 alignment tool and the PB0656A pilot bearing. A release bearing is not included, so buy a new throwout bearing that matches your fork and bearing retainer.
• Pull the old pilot bearing or bushing from the crank with a puller like the OTC 7318 pilot bearing puller, and clean the bore.
• Resurface or replace the flywheel; our resurface vs replace guide explains when machining is enough.
• Center the disc with the supplied tool or a clutch alignment tool kit, then tighten the pressure plate bolts evenly in a crisscross pattern.
• Lightly grease the fork pivot and bearing retainer. If the bellhousing has been swapped or the car shifts poorly, check bellhousing bore runout with a dial indicator and magnetic base. Then adjust the linkage to factory pedal free play.
• Check the gearbox oil level and type while the transmission is out. If you are freshening a four-speed at the same time, see our Muncie four-speed guide.
• Break the clutch in gently for the first few hundred miles. See our clutch break-in guide.

The kit is new, in stock and ships from the USA the same business day with a 1-year warranty.

Does GM8-HDSS fit a 1973 Firebird?

ACT's fitment table lists the 1971 through 1974 Pontiac Firebird Base with the 5.7L V8 and a 10.5 inch clutch. Measure your flywheel face and input shaft to confirm the car still has the original setup.

How much torque does it hold?

ACT rates GM8-HDSS at 629 ft-lb measured at the crank, 32 percent over the original clutch.

Does the kit include a throwout bearing?

No. It includes the pressure plate, disc, alignment tool and pilot bearing. Buy a new release bearing that matches your fork and retainer.

Will the pedal be harder than stock?

Somewhat. ACT expects its Heavy Duty plates to raise pedal effort by about 15 to 40 percent depending on the application. Fresh linkage bushings help a lot.

Is this clutch OK for street driving?

Yes. ACT recommends it for street and race use and describes smooth, positive engagement with an organic disc.

What if my car has an 11 inch clutch?

This kit is a 10.5 inch clutch. A car with an 11 inch flywheel and bellhousing needs a different kit, so send us what you measured.

• Transmission Slipping Diagnosis Guide
• Shift Flare vs. Slip: How to Tell the Difference
• Automatic vs. Manual Transmission Repair Cost: What to Actually Expect