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I have a 85 bronco with a 351, 5.8l. I want to swap to a GM hei distributor. There is a red and green wire on the old coil. Once I spliced on to new pigtail for the hei, the tach pegged all the way over. Does any buddy know how to correct this so I can use my stock tach ?

Is my post being seen. I have got no replies?

I’ve been watching but I don’t have any answers. Also curious.

Your missing the ground wire to the hei believe black with green there will be two ground wires for the hei to make the tach work. I have more details if you can’t find it text me 7146141097

The distributor cap should have markings telling you how to connect. You need two grounds internally, and external ground, positive power (with key on) and coil (-).

I don't have any images on me now but can circle back. Post photos and I'll help.

This is a large cap, i.e. coil in the cap type HEI with the 4 wire module screwed to the dist body under the cap?

If so, then there is the pigtail going from the module to the cap and then there are two contacts in the cap for external wires. One of them should be labeled "TACH" on the cap. The other is Ignition power. Buy the correct connector as it will have the clip to hold the wire in place on the cap. These HEI's are power hogs, the OEM wire in a GM install is 10 or 12 gauge wire. Suggest that you use a relay switching battery power and driven by the stock ignition power wire. There is no ground wire on these distributors, they ground thru the body of the unit.

If this is not that, then we need to know more about what you have. A picture would be good.