On 11/16/2021, Peter Todd in Australia wrote:
"I needed to position the 3 dowels on my machined flywheel to mount the MGB HD Diaphragm pressure plate, but when I sat the pressure plate on the flywheel with the bolts fitted not quite tight, I could jiggle the pressure plate around almost 1 mm. I bought six 5/16 UNF Allen headed countersunk screws, That enabled me to mount the pressure plate on the flywheel by using the tapered headed screws to accurately position it centrally. The three dowel holes were drilled using a pedestal drill with 10mm spacers under the ring gear to prevent the flywheel from rocking. Next step is to get the flywheel and pressure plate balanced both singly, and as an assembly". -- Peter

On 11/23/2021, Frank Netterberg wrote:
"The MGB diaphragm clutch is the way to go. Beware of the very early model - the release plate was only held by a circlip and it came loose. The straps fastening the pressure plate to the cover were also weak points. The competition MGB clutch requires a much harder push and gives a rather sharp takeoff. Maybe the standard MGB clutch is good enough provided the linings on the driven plate are both bonded and riveted. The linings on the standard MGA driven plate are only riveted and come off at Twin Cam revs. Just strengthening the coil springs on the standard coil spring clutch is not the way to go. The Twin Cam coil spring clutch gets out of balance after about 10,000 miles of hard use even with the strengthening spider. This was one of the causes of the engine vibration which caused the petrol to foam in the rear float chamber, lean running, and holed pistons. Both Bob Olthoff and Peter Wood told me it was the cause, which the factory never identified". -- Frank

On 11/23/2021, Bill Spohn via groups.io wrote:
"Anyone contemplating the MGB diaphragm clutch conversions should always mate the gearbox to the engine after the clutch is in place (tighten the bolts) and try to turn it over. Some MGA front cases foul the wider clutch cover and need a little grinding (usually not much) for clearance.
If you find that the engine is locked solid to the trans, let all of the bolts around the bellhousing off a half turn and try again. repeat until the engine will easily turn and by that time you will have marked the inside of the front housing and will know where to grind a bit away and try again.
And don't forget to follow Barney's instructions to convert to MGB front trans cover and release bearing and fork"! -- Bill

On 11/26/2021, Frank Netterberg wrote:
"Although, in 1970 I had a meeting, arranged with Syd Enever who said he was "mystified" about the vibration, but would get Alec Hounslow to attend the meeting. However, he suddenly cancelled the meeting with no explanation! And would not take my calls.
With 8.3 pistons, centrifugal advance only, relatively low octane fuel in the 1960s, and much high speed and high revs running on the track and before the days of open road speed limits I never had holed pistons but only a severe vibration at around 5 000 rpm. This was then a comfortable, long-distance cruising speed of about 90 mph, so I had to go slower or faster to avoid it. Maybe I was lucky as most of it was at an altitude of 4000 - 5000 ft. My car was one of the last few CKD assembled in 1960 in South Africa) and came with the 8.3 pistons, etc.
As I understand it, the factory never managed to hole a piston on a road or track car. Maybe it was because they were all fairly new and had less than the approximately 10 000 miles of hard use for the coil spring clutch to get out of balance? In the third edition of the Service Parts List the clutch is listed as a N.S.P (non-serviceable part) and could only be supplied combined with the flywheel and crankshaft all balanced as one unit! I had this balancing done when the car was restored with a MG competition clutch and it is relatively vibration-free. However, the car is no longer driven as it was in time of yore. The carbs are also now flexibly mounted as specified by the factory for highly tuned pushrod motors". -- Frank