Alternative Clutch Set-Up
By Mark Lambert
Originally published in the Austin-Healey Magazine, June 1996
I recently completed some clutch work on my BN2 and I’m pleased with the results. Did you know that the entire clutch pack (flywheel to throw-out bearing) from the late 3000 (BJ8) will fit any of the earlier cars from the BN2 forward? Neither did I, but I had a hunch.
Over the past two years, I have made several adjustments to this car’s mechanicals. Beginning with a nicely sorted-out car, freshly restored to original specifications, the best results are gained by focusing on one system at a time while experimenting with variations from stock specifications. While very comfortable to tour in, being cool and nearly vibration free (see Heat and Vibration article, Austin-Healey Magazine SEP 93), its only disagreeable symptom was a slight laboring through low-end acceleration. I theorized that the immense weight of the flywheel was the cause.
The 100-4 and the 100-6 have the same massive 40 lb flywheels. Why? My guess is cost savings. Using this heavy flywheel Austin avoided the expensive process of balancing the engine’s internal components. I strongly recommend balancing these components as part of any rebuild. This will allow the use of a substantially lighter flywheel improving low-end performance and throttle response. I do not, however, recommend shaving flywheels or permanently altering any system on the car. Always allow for the change back to original specs.
The late 3000 clutch pack is a good substitute for the original on a balanced (100-4, 100-6, or early 3000) engine. It’s nearly 20 pounds lighter and uses the vastly superior 9-1/2 inch diaphragm spring type pressure plate. The diaphragm pressure plate is much smoother and has twice the life of the old three-lever pressure plate.
I began this job by removing the transmission, clutch and flywheel. Bolting up the 3000 flywheel (all big Healeys have the same bolt pattern) with a fresh 9 ½” clutch disc and pressure plate, I took only the bell housing (separated from the transmission) and slipped it into position on the back of the engine, securing with the two long shank bolts in their appropriate holes. Turning the engine by hand (spark plugs removed) while looking through the main shaft hole in the bell housing, I confirmed there was plenty of room for the BJ8 clutch pack.
Two important notes: 1) Two long shank bolts (frequently missing or in the wrong holes) are used to position the bell housing onto the rear engine plate in all big Healeys. These bolts fit into the two slightly smaller bell-housing holes at the 11 o’clock and 5 o’clock positions and should be installed first. 2) Never mix clutch pack components.
Whichever setup you choose, use it all, including the proper throw-out bearing. Otherwise, the clutch geometry will be incorrect and the mechanism won’t work properly.
One more simple change you can make to improve the BN1 and BN2 (applicable to all big Healeys): Replace the original type rubber transmission tie rod bushes with urethane ones. The rubber ones, upon becoming oil soaked, soon lose their resilience, and turn to gum. If your BN1 or BN2 has a grabby clutch, this is probably the cause. The BN1 and BN2 clutch linkage levers off the chassis. If these bushes are bad, the entire engine and transmission unit will move. Depress your clutch pedal with the hood open and watch the engine to check for this. If the engine moves, it’s causing loss of control upon clutch take-up.
The end result is a clutch just as smooth as a hydraulic unit. The low-end response has improved tremendously. Gone completely is that truck take-off feel common to the early big Healeys, yet the car still accelerates smoothly from as low as 800 RPM in third gear.
Feel free to call me at the shop with any questions. Happy fly wheeling.
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