I think it is because the instructions don't say to do anything with the brown wire. Pink goes to the MSD red, and the module is removed and replaced with a harness (2 wires) that go to the magnetic pickup wires. Orange and black go to the cap and so does a ground. White wire is not used.

With the 7-pin HEI, the white wire goes to the brown... should I just plug the brown wire back into the cap?

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

There is something in the instructions that speak directly to this. Sorry, I don't have mine here in front of me. But, I read them the other day and I specifically remember it saying that you would have to add an extra part to get the tach to work on some vehicles.

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'86 IROC-Z, 305 LG-4, T-5, T-Tops, 50k Original Miles, K&N Air Filter, Jet chip, KYB Shocks/Struts, Centerforce Dual Friction, B&M Ripper Shifter

 

That is for 5-pin HEI if you experience a hesitation or something you need to order a diode... and I don't see anything for the brown wire on that diagram either.

If I plug the brown wire in... what could I fry?

 

Where does the brown wire come from (or where did it go to)?

Check out page 7 of the book; it talks about inoperative tachometers- you might need a filter (what Sgt Sweet was talking about). You might instead need to bypass the GM tach filter; I'm not sure where that is since I have an aftermarket tach.

The 7-pin HEI is a different animal; it's not wired for a magnetic pickup. Give MSD a call before you hook that brown wire to anything, and let us know!

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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

[This message has been edited by TomP (edited January 08, 2001).]

 

I wrote to MSD, but it usually takes them a few days to reply. I just want to make sure that I am not screwing things up by not hooking it up properly. I don't care so much about the stock tach because I am replacing it soon anyways, but I don't want to screw up my coil.

The brown wire used to plug into the cap right next to the pink wire and behind it were where the 3-wire harness went from the magnetic pickup from the base to the cap. It goes to a diode or something that is bolted to the firewall and I assume goes to the tach. In fact, I think it says tach on the cap where it plugs in normally...

MSD's instructions only show pics for the pink wire (to red) and (although not so detailed) replaceing the 3-wire harness/module with the 2-wire harness for the magnetic pickup.

 

I got the harness for my TA but on my fiero wich has the same style coil I hooked the white tach wire in with the white wire connection to the MSD and it all behaved normally.

 

The tach wire either needs to be connected to the negative side of the coil without the stock filter(some cars have them some don't) or to the tach output of the MSD. My tach worked fine hooked up to the MSD.

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter