Tachometer reading too high

[Relax360]

almost done with my 67 Barracuda have it running but i noticed somthing the other day. The reproduction tach rests at zero with the car off but once you turn the key to the on postion it jumps up to 500 even before you start the engine. after you turn it on it read about 500 rpms too high at idle. Haven't tested it at other rpms.

I am running an MSD 6AL 2 box. MSD billet distributor. I don't have a tach adapter not sure if i need one. Just trying to figure out what I can do before i remove the dash. Any thoughts? The tach is from year one.

 

[RustyRatRod]

If the tach is switchable from 4, 6 and 8 cylinder, make sure it's switched to 8.

 

[Relax360]

thanks stroker we actually had the problem before i better double check the box.

 

[mod5v]

I believe you need a tach adaptor avalible from msd for your setup.

 

[Demonracer]

In most cases you need the MSD tach adapter when running MSD electronics.

 

[pishta]

Here you go...uh, its in the instructions...

TACHOMETERS
The MSD Ignition features a Gray Tach Output wire that provides a trigger signal for tachometers, a
shift light or other add-on rpm activated devices. The Tach Output wire produces a 12 volt square
wave signal with a 25° duty cycle.
Some vehicles with factory tachometers may require a Tach Adapter to operate with the MSD. For
more information on Tachometers and MSD Tach Adapters, see the Tachometer Section on page 7.

CHRYSLER needs white wire hookup = 8910 or 8920 with magnetic trigger

 

[Relax360]

thanks guys just ordered an adapter hope it fixes the problem