Missing Link Between Horsepower and Acceleration?

Clutches for Increased Torque Applications

• 4 Cylinder, 215mm Clutch
  The 215mm clutch assembly is adequate for 4 cylinder engines with torque output of 150lbs. or less. Buyers of 2200 engines use this pressure plate or convert to the 228mm clutch assembly.
• 4 Cylinder, 228mm Clutch
  Early 4 cylinder 2002's and up to 1973 and all tii's used a flywheel that would accept a 228mm clutch assembly. Cars built after this can adapt to this flywheel by changing over to the earlier 28mm long flywheel bolts (215mm flywheel bolts are 22mm long). Our point is that any 4 cylinder engine can end up with this 228mm clutch! The Metric Mechanic HiTorque Clutch Assembly consists of a 228mm HiTorque pressure plate with clamping pressure greater than the legendary tii pressure plate. This pressure plate takes a shorter 42mm throw out bearing when used with a 4 speed (232 Getrag) or a shorter 25mm throw out bearing when used with a 5 speed (245 Getrag). The clutch disc we use has a non-asbestos woven liner. This disc has an improved coefficient of friction, i.e. grabs better and won't glaze over as did the earlier pressed discs with the brown "fiber board" appearance.
• 6 Cylinder, 240mm Clutch
  Six cylinder engines with less than 240ft. lbs of torque require our HD pressure plate - 15% more clamping pressure and 6 strapping bands. This pressure plate is typically used with our 3500 engine. The main problem with 6 cylinder clutches is that, under high torque applications, the strapping bands that hold the pressure plate together will break! The stock BMW pressure plate uses a total of 6 strapping bands. On the M5 & M6 clutch, 9 strapping bands are used. On our Metric Mechanic HiTorque clutch, we use 15 straps. In addition to this, we increase the clamping pressure by about 15% over a stock BMW clutch. Again, we use an improved asbestos-free woven liner disc. This clutch assembly should be used with any 3800, 4000cc engine or turbo engine. Running these engines on a stock clutch will cause the pressure plate to come apart in less than 600 miles (1000 kilometers). Going to an M5 or M6 clutch will only slightly postpone this failure. Many M5 & M6 owners will order up our clutch assembly because the stock M clutch usually only lasts about 20,000 to 30,000 miles under aggressive driving.

Pilot Bearing
Whenever an engine or transmission is pulled, the pilot bearing should be inspected.

• Needle Type
  Needle type bearings used on '77 and later BMW's should be repacked with a high quality grease. These bearings have a tendency to fail. When this happens, the needles often mutilate the end of the pilot shaft. We have a needle bearing set-up that repairs this problem. This bearing comes with a thin inner race (sleeve) that goes over the end of the damaged pilot shaft and should be secured with red or green permanent thread locker.
  
• Ball Type
  On earlier ball type pilot bearings, we replace this bearing with a more up-to-date seal ball bearing so that the grease won't leak out of it.
  Note: To remove the pilot bearing, refer to the "Pilot Bearing Puller" in the section on Tools.