MSD 6A & factory tach

[hemi68charger]

Hey gang..
Finally resolved the MSD-6A non-firing issue I had on my buddy's '71 v-code 440 Challenger R/T. We'd like to get his factory tach to work as well and I see there are numerous adaptors for this that MSD sells. I'd like to get suggestions and ideas from you E-body owners who have already gone down this road. I have the box mounted under the battery tray and if I'm not mistaken, there's a "tach" port on the side. Right now the OEM tach lead isn't attached to the - side of the coil, didn't want it to mess around with the electrical system when we 1st fire it up.

Any suggestions on working configurations you all may have?

Thanks in advance..
Troy

[dodj]

I bought the MSD tach adapter for mine. Works fine. It's an 8290 or something. I will look tonight and get the correct number for you.

[dodj]

Well.....I had all the numbers but in the wrong order. It's an 8920 tach adapter. 

[HP_Cuda]

Sweet!

Note to self.

[KillerBee]

If the tach hasn't been rebuilt/calibrated I would suggest testing it's accuracy first.

Most factory tachs including mine are off by a fair amount through the entire RPM range.

I plan to use one of the E-body repop factory tachs from Charger Specialties.

They claim their tachs will work with MSD ignitions with no adaptors needed.

I have heard good reviews for them.
I have never priced having a factory tach restored and recalibrated but $199 sounds pretty good for a brand new factory looking tach with modern electronic internals.

 

http://www.chargerspecialties.com/tachos.htm

[venture]

Any suggestions would be appreciated. I am using the 8920 adapter on a 1974 challenger  and folowing their diagram, with advice from an msd tech. Quote, "Rally tach will nor recognize the 12 volt square wave signal that is coming out of either wire. Hook up the 8920 to the gray wire from the ignition box only." Following the diagram supplied with the 8920 adapter, black to - ground, violet is not used. white to gray wire from msd 6al, red to + side wire from original coil. Now in the shop manuel shows the orginal wiring for the tach hooked to black wire with yellow tracer,, which happens to be the negative side of the coil. I have yet to hook that wire up, going to try it soon. So far the oe tach does not work.

[dodj]

How did it work out for you? 

[venture]

Tried that yesterday tach still does not work, think it must be the tach, the tach worked the last time the car was fired, that would be 34 years ago, but with time, maybe the tach is shot. Going to have to find a tach to try to make sure.

[hemi68charger]

thanks guys... We finally fired up the motor a few weeks ago. I haven't gotten to the point of wiring the tach in ( factory is already installed in the dash, just need to get the adapter going).

Any suggestions on a discrete place to mount the adapter?

[dodj]

I mounted mine inside the steel frame by the ashtray. Siliconed on.