Connecting MSD to Stock Factory Tach Rallye Dash '70 Barracuda

[Mopsquad]

Just completed my EFI conversion on the dual TB 426 hemi.  It uses an MSD 6AL for an ignition and it supplies a gray wire for a tach output.  How do I connect it to the existing tach on my '70 Barracuda?  It probably will need a conversion adapter but what wire under the dash (the MSD is inside the car) is the source wire to connect to?  Or, is there a wire in the engine comp't that I can use?

TIA,

Steve

[Chryco Psycho]

MSD sells a tach adapter , you will need this to make it work
The tach wire is grey you could be able to put the adapter under dash & connect to the grey tach wire before it goes through the firewall to the coil

[Chryco Psycho]

https://www.summitracing.com/int/parts/msd-8920/overview/

[Mopsquad]

MSD sells a tach adapter , you will need this to make it work
The tach wire is grey you could be able to put the adapter under dash & connect to the grey tach wire before it goes through the firewall to the coil

So the stock wire from the tach going out from under the dash is grey? Is it in a certain location(under the dash) that I should be looking for it?

[7212Mopar]

I just finished this installation but my MSD box and tach adapter were mounted in the engine bay. The factory has a single tan color wire from the back of the tach through the firewall and connect to the neg terminal at the coil. You can intercept this wire inside the car and tape off the end in the engine compartment if you want to retain factory wiring. Do not connect to the coil. The only two wires connected to the coil terminals are from the MSD box.

[Mopsquad]

I just finished this installation but my MSD box and tach adapter were mounted in the engine bay. The factory has a single tan color wire from the back of the tach through the firewall and connect to the neg terminal at the coil. You can intercept this wire inside the car and tape off the end in the engine compartment if you want to retain factory wiring. Do not connect to the coil. The only two wires connected to the coil terminals are from the MSD box.

Thank you.  I'll look for that tan wire under the dash. 

[Chryco Psycho]

https://forum.e-bodies.org/electrical-and-audio/11/colored-wiring-diagrams-70-cudachallenger/1349/

The wiring diagrams here clearly show the grey wire to the coil - terminal

[Mopsquad]

https://forum.e-bodies.org/electrical-and-audio/11/colored-wiring-diagrams-70-cudachallenger/1349/

The wiring diagrams here clearly show the grey wire to the coil - terminal

Those diagrams are very helpful. Thank you.

[1 Wild R/T]

Gray Tach Wire should be in location 20..  The schematic shows the wire going through a grommet on E bodies but I've never seen that.... 

[Chryco Psycho]

different years were in different places

[Mopsquad]

Gray Tach Wire should be in location 20..  The schematic shows the wire going through a grommet on E bodies but I've never seen that....

I'll check it out referring to that schematic.  Appreciated.