I installed a 6AL box over the weekend and now my tach doesn't work. I wasn't sure if I needed to get an adapter to plug into the MSD box. I tried troubleshooting but I could never get the tach to work. My biggest confusion is which wire triggers the tach reading and how it has to be connected so my factory tach will work again. Thanks, Josh

There's a spade terminal recessed into the end of the box that drives the tach. Run a wire from there to the tach wire (I think it's black).

You may have to get a tachadapter from MSD to get it work over 4000 rpm.

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GTA -89:383, 4-bolt,Free flow muffler,dual 3" HF cats, Edelbrock headers, Canfield heads, 1.52 RR 7/16, ZZ-9 cam, Big Mouth, AS&M LTR, !plenum, 52 TB, MSD 6AL, TPIS level V prom, Superior shift-kit and all the minor mods,looking for a SR ...
http://www.itv.se/tacs/members_cars/m279/m279.html (Swedish Trans Am Club)

99.99% chance you don't need an adapter. State what year vehicle you have so that we know what style ignition you have.

check out this link for the problem I hjad with the MSD and tach:

http://www.thirdgen.org/messgboard/F...ML/001362.html


James

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1985 Z-28, 350 TPI, T-Tops, edelbrock 6085 heads, ZZ4 cam, accel base/runners & 24 lb/hr inj., ported plenum, everything gasket matched, crane AFPR, SLP 1 5/8 headers, single 3" flowmaster catback, 3" Catco cat, modified tranny, 165 ECM & ARAP code, MSD 6AL/wires, edelbrock STB, Spohn SFC, GW "wonderbar"

Josh,

You should not need any adapters to make the factory tach work. Depending on the year of the car, all you need to do is bypass the tach filter in the factory harness to make it function. Generally with in about 1-2 feel of the coil on the tach wire there will be a 1x1 inch cube with a white wire going in and a white wire come out. This is the tach filter, bypass this and hook the two white wires together and then hook the tach wire to the white wire of the MSD box. the tach will function with out any problems. If this is an early 80's car the tach filter may be on the firewall between the brake booster and the valve cover, this style will look like a points condenser. Same thing applies here bypass the filter and your off and running.

Thanks,

Joe
MSD tech

I have an '87 IROC.

Thanks for all the info. MSD Tech, so there is no need to connect the tach output terminal on the box to the wire going into the firewall to the tach?

Thanks, Josh

You can hook it to the tach output but it will also work off of the white wire. Either place will be fine.

Thanks,

Joe