B48 / B58 Alternator Overrun Pulley

The Alternator Overrun Pulley for the B48/B58 allows the alternator to freewheel when the engine is trying to decelerate. This has many benefits. It saves your crank balancer from trying to tear itself apart and also makes the engine run smoother and shift more rapidly. Longer writeup coming soon. 

Fits all B48 and B58 NON 48V alternators.

Also fits the Alternator of the B48C transverse engine in the MINI as well as the B38 however there are many variations of this engine in different chassis so we have not been able to verify every possible variation. 

There are many variations of the correct alternator but if the following is called out for your car in realoem then it will fit:

•  12318634167 - B48 and B58 (330i, 340i etc)
• 12318627125 - F56 Mini and other Transverse B48s

To install - 

• Detension belt
• Remove plastic cap in center of alternator pulley
• Hit nut inside current pulley with impact gun to spin it off
• Remove old pulley
  
• Thread on new pulley (we do not recommend loctite)
• Hold center of alternator shaft with a torque wrench in the off (counterclockwise) direction - the alternator shaft is a 10mm 6 point hex (do not use 12 point). Hold Strom Overrun pulley hex with 27mm open wrench and tighten to 38lb/ft - 50Nm
• If you do not have a torque wrench that can go in the off direction then hold it with a normal wrench and make it nice and tight, it is not a critical torque spec and the pulley will self tighten in use as the alternator spins and loads. 
• Reinstall belt
• If you don't understand these instructions then do not install this yourself and have a mechanic do it.