Alfa Romeo Pressure Plate Conversion
I was driving the Squire to work when some butthole cut me off, and about ran me off the road. During the course of my avoidance manuevers and maniacal downshifting, I somehow jammed the throwout bearing past the spring arms of the original pressure plate and up against the clutch disk. This is not a good thing to do, and was the probably result of my having the clutch pedal "moderately" out of adjustment.
Several things happened at this point, most of them noisy, none of them good. The stock, long style pressure plate fingers grabbed the throwout bearinig and bent themselves into uselessness. After a few seconds, the throwout bearing worked itself loose and normal operating sound resumed. However, when I tried to depress the clutch, loud grinding and grating noises began. It was clear that, while the pressure plate was gripping the clutch disk tightly, the throwout bearing had retired from active duty and no amount pedal pushing was going to make it let go. I said some words, and popped the car into neutral and coasted to the side of the road to think and cool off.
Having owned a Corvair for many years, driving clutchless is not much of a challenge. Corvairs regularly surprise their owners with snapped clutch cables, a rarely mentioned problem but not an uncommon one.
I was only a few miles from home, so I put the car in first and started up in gear. After a herky jerky second or two I was off. Up-shifting clutchless is no problem on a synchronized tranny, and the T5 is easier than most (it turns out). The only problem is stoplights. Here, it's slow down in gear, pop the car into neutral, and kill the ignition. Then start up in first gear when the light turns green. Anyway, I got home and took the Corvair to work.
I have another rebuilt stock pressure plate still in the box, but last year, while working on the Alfa, I noticed that the Ford 8.5" flywheel and the Alfa 215mm flywheel looked nearly identical. I measured everything with an eye toward a modern pressure plate option. The results were that the Alfa flywheel was only
0.125" shallower (0.123" is specified as stock) than the Ford flywheel.
Update - The correct stock depth of the Alfa flywheel cup is .878". Mercedes flywheel cup depth is .885".
Update - After 90-100k miles of trouble free Alfa pressure plate use, the Squire needed a cluth job. I replaced the Alfa pressure plate with a Mercedes 190E plate (SACHS Part # 3082164031), MUCH cheaper.
Below is an excerpt from a flywheel resurfacing bulletin, showing correct stock cup depths. Trim your flywheel accordingly.
FLYWHEEL SPECIFICATIONSThe AERA Technical Committee suggests referring to the following
flywheel specification chart when re-surfacing flywheels.Manufacturer Dia., Flywheel Specs Comments_________________________________________________________________69-74 Alfa Romeo 215mm, Cup .878" 1750, 200060-65 Ford, Falcon 8.5", Cup 1.00" 6 Cylinder engines85 Mercedes, 240D 215mm, Cup .885" 2.4l Diesel engine
85 Mercedes, 190E 215mm, Cup .885" 2.0l, 2.3 SOHC engine (not DOHC)
(excerpted from) The AERA Technical Committee - June 1992 - TB 677R
Saturday afternoon I dropped out the T5 and pulled the flywheel/pressure plate/clutch disk off. I took the flywheel down to the machine shop and had .15" turned off the plate mounting face (see above chart for correct measurements - I took off slightly more than stock due to clutch disc thick/thin differences). I picked up a new Sachs 215mm Alfa Romeo pressure plate, modified a new S10 throw-out bearing (I'm using a stock S10 T5 tranny), bought a new clutch disk, and I was in business. Everything went back together smooth, just like a regular old clutch job.
During reassembly, I relocated the Z-bar rod pivot up a few inches (top picture) to reduce pedal travel. The diaphragm pressure plate setup, in addition to the relocated pivot point, made a huge difference in the pedal effort and travel. With the old long style plate, working the clutch was like having a one leg nautilus machine in the car. Now pedal effort is very light, almost new car light.
I also drilled and tapped one size larger pressure plate holes, and used ARP shoulder bolts.
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