Which way to wire MSD on 77 Z?

[Guest steves280]

I'm wiring up an MSD 6A on a 77z that already has working SDS injection. Any advantage to using the mag trigger wires directly from the dizzy instead of just using the white wire type setup via the old OE spark box? Is there anything bad about the OE spark box that would make it worth bypassing it totally from a performance standpoint, like bad signals at high rpm etc? I have SDS so the EFI isn't a problem either way and I know how to deal with the tach. But if there is -no- advantage to bypassing the OE spark box, the white wire setup is easier, everything else is working and I'll still have the old box in the loop in case the MSD craps out... This is a street car, pretty warm motor, revs to aprox 7000. TIA for any advice.

[srgunz]

That MSD magnetic wire is used only for crank fire set ups, not yours.

Wire using white wire according to the diagram that says amplifier style ignition. No wires will go directly to distributer. It should work fine.

[Guest bastaad525]

That MSD magnetic wire is used only for crank fire set ups' date=' not yours.

Wire using white wire according to the diagram that says amplifier style ignition. No wires will go directly to distributer. It should work fine.[/quote']

 

 

Not true. You CAN run it off of the mag pickup wires from the distributor. When I had my N/A motor running SU's, I was running the '81 N/A distributor, and was running an MSD 6A. What I ended up doing was taking the ignition module off of the distributor, there are two wires that go into the module from inside the dizzy, a red and a green one. I connected these to the purple and green wires from the MSD and it worked perfectly.

 

 

here is a link to my old topic over at zcar.com when I finally figured out and posted exactly how to wire the MSD into the car:

 

http://www.zcar.com/forums/read.php?f=1&i=287734&t=287734

 

however, I will say that I did this because, for some reason when I installed the MSD using the white wire method on the 240z, it didn't work. BUT, when I had that same motor in the original '81 ZX with all stock EFI, I had the same MSD box wired up using the white wire and it worked fine. So I'm gonna guess with '77 you'd be fine using the white wire and probably should, but since you're using SDS instead of stock EFI, I dunno if you need the ignition module or can remove and bypass it as I had.

[evildky]

remember the 77 dist is very different from the 81zx dist, I have run 71 points, 78 elec, and a later zx dist all with a msd box, seems to me the 78 used the purple and green wires if I recall correctly to the msd box then the msd wires streight to the coil and I had an aftermarket tach so I'm not sure what you'll need there and I've not had an sds to play with so I can offer nothing there

[Guest bastaad525]

yeah I'm not really aware of exactly what's different between the earlier and later electronic dizzies. And I did need to run an aftermarket tach as well, though I believe this was because I have a '72 240... I think with a later 280 you CAN wire it up to work with the stock tach.