'60s Era +4 Clutch Information
©By: Greg Solow's Engine Room
125 Front St.
Santa Cruz, Ca. 95060
Originally written: October 1998
Last update: June 15, 2009 - Reformatted page
In response to a question about the clutch in the +4 Morgans being similar to that used in the TR3s and 4s. Greg Solow wrote:
Sorry, but the pressure plate was either unique to Morgan, or Morgan was the most common application. It is like a TR-3 pressure plate with a thrust plate for use with a Carbon release bearing. The Austin Healey 100-6 pressure plate was similar, but I believe had a sightly different spring pressure. When we replace clutches on Morgan +4s, we usually recommend converting to a 8 1/2 inch diaphragm clutch. It requires less pedal effort, operates more smoothly, weighs less, and applies more pressure to the clutch disc. The flywheel must be redrilled for the pressure plate, or you can find a TR-4A flywheel which is already correctly drilled.
The redrilled flywheel should be rebalanced with the new pressure plate attached.
The release bearing must be very accurately positioned by the hole bored in the bell housing. This hole tends to wear in the vertical direction because of the force exerted upward by the release bearing sleeve operating pinion at the bottom of the sleeve. We have designed and built a jig in which we bore out the worn hole, shrink in a steel sleeve, and then bore and hone the sleeve to the proper size for the release bearing. After this operation, the release bearing is held in exact alignment with the center of the thrust plate which is "crimped" onto the diaphragm spring of the pressure plate. If the release bearing is not in the exact center of the pressure plate, there is a tendency for the oscillating contact between the thrust plate and the off-center release bearing to cause the thrust plate to work loose from the pressure plate diaphragm spring. This often occurs in cars that use diaphragm pressure plates as original equipment when the mechanism that locates the release bearing wears, allowing the bearing to shift away from its original "centered" position. The release bearing sleeve also has to be modified to compensate for the difference in the height between the diaphragm and coil spring type pressure plates.
Although this all may sound very involved, it is a very worthwhile
(John T. Blair writes:)
While I have a 4/4, it was nice to see someone that could support the +4 community. So I had to ask.
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