I'm trying to install a 911 '75 tach in a '79 930. The tach won't read. According to the Clewett site the older tachs are high voltage. Will your device do the same thing as the Clewett adapter.
Tach adapter [10000] - $99.00 : Clewett Engineering, The complete solution for ignition & fuel injection.
The tach works fine on my '86 3.2 w/eletromotive hpv1.