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Old 12-25-2021, 01:31 PM
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Elarson Elarson is offline
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Default HEI Tachometer Questions

My project car is a '75 Formula. A previous owner added the MSD Super HEI kit (good) but apparently didn't know how to make it work with the factory tach so they put in an aftermarket tach (yuck). So I need a little help getting the factory tach to work by using an MSD tach adapter. I need:

1) what is the color wire that originally connected the HEI to the factory tach? I'm assuming I'll find it somewhere, with the end clipped off.

2) did the factory tach trigger off the coil (+) or coil (-) terminal?

Thanks,
Eric

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  #2  
Old 12-26-2021, 11:07 AM
78w72 78w72 is offline
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the tach wire was a separate harness from the main harness. its a thin gauge brown wire in the engine bay usually with a inline fuse, then after the firewall was merged with a 2nd wire for 12v that is red or pinkish with a black stripe & connector for the 2 prong at the tach. cant say for sure if it was + or - coil trigger but on the stock HEI there is only one connection for it next to the 12v wire, pretty sure its -

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Old 12-26-2021, 06:31 PM
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Elarson Elarson is offline
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Thanks for the info.
Bad news....my factory tach harness is missing.
Good news....Ames sells a reproduction tach harness. Problem solved.

Eric

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