Msd Tach Adapter 8920. - Pelican Parts Forums Msd Tach Adapter 8920. The tach can be connected by running a wire directly from the new MSD unit tach output, to the black and purple stripped wire side of the white connector for the old tach connection in the engine compartment. _____ Rex 1975 911s and 2012 Range Rover Sport HSE Originally Posted by 1976 TN Porsche.MSD Wiring in 66 - Pelican Parts Forumsmsd wiring - Page 2msd wiring - Pelican Parts Forums1977 911S MSD 8920 tach adapterSee more results Porsche 911 MSD Ignition Unit Installation | 911 (1965-89 wwwcanparts›Porsche HomeThe tachometer wire inside the CD box connector is black with a purple stripe down the side. This wire needs to be connected to the tachometer output on the side of the MSD unit. In addition, the tachometer adapter from MSD needs to be installed inside the engine compartment.