70 tach to 79 cdi?

[jhelgesen]

Will the signal from a 79 cdi box work with a 70 tach? I have to pull the 4cyl tach from the 912e and put a 6cyl in. I've got a 70 911t tach on the shelf.

70's get the signal from the distributor, while the 79's get the signal from the cdi box.

Thanks!

[Early_S_Man]

John,

There is a chance it will work. Some early tachs do work, others ... not!

If you know the 911T tach is functional, a simple buffer circuit [$20 in parts] with a handful of components on a small Radio Shack breadboard should be all that is needed if the '70 tach doesn't read correctly with the SC CDI unit.

[RoninLB]

Originally posted by Early_S_Man
a simple buffer circuit [$20 in parts] with a handful of components on a small Radio Shack breadboard should be all that is needed if the '70 tach doesn't read correctly with the SC CDI unit.

isn't that what either of the 2 MSD tach adapters do ?