EZ-EFI tach signal

[eventhorizon66]

I am considering the making the switch to EZ-EFI, but would first like to get a good idea of what it's really gonna take to get it installed and running. I have an MSD Pro Billet HEI which has a tach output wire coming directly off the module. Would this provide an adequately "clean" tach signal (equal in quality to that from a CD ignition)?

[bluzman2004]

On most HEI distributors, the TACH signal that comes out is actually just connected to the negative side of the coil. It's not a clean 12 volt pulse. On that MSD one, you should probably contact MSD and ask them if it outputs a 12 volt pulse like their 6AL box or is it designed just like the standard HEI distributors. There are somany different types of distributors out there that it's impossible to keep track of them all. That's why the instructions suggest an aftermarket ingnition box. It just puts everyone on the same playing field. If yours is built like the standard HEI, you will be able to use the included TACH adaptor module with that. If it outputs a 12 volt pulse, you can just plug directly into it. Either way it will work out for you.

[eventhorizon66]

When I'm ready for this system, I will likely keep my HEI, but upgrade to a 6AL to replace the internal module. Thanks for the thorough response.