1973 Mach 1 Build

I've got a '73 mach 1, 351c under the hood. It was my father's build years ago that I recently inherited, ran great back in the day but I've run into some issues I was hoping I could get some help with.

the initial reason the car stopped running years back was because the MSD 6al box was shot. I went through the motions and replaced that, along with the spark plugs, the wires, coil cool and distributor. after that I did replaced a faulty fuel pump, swapped the battery and standard maintenance like changing all the fluids.

I'm getting a solid 12v when the key is in standby, but when we try and turn it over it drops down to 6v or so, and on the rare occasion it actually starts it drops to 4v and then sputters out.

I'm getting fuel, I'm getting spark, there's no iasues with the Holley carb that's in there. my mechanic is suggesting a brand new wiring harness, which im picking up soon. I was wondering if there was anything we could be overlooking? he said hes never seen anything like that before.

I'm not too savvy with mechanical work myself, but it's my dream to get this car up and running so any help at all would be much appreciated.

The Shemdogg said:

Sounds like a bad ground somewhere. Are you measuring voltage at the coil or battery?

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I was measurung at the coil, is there somewhere else i should be checking it at?

rustaddict said:

So you went back with a new MSD 6 series box? Are you still using a ballast resistor ? Where are your red wires and your ground wire hooked to from the MSD box?

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yeah I went with the same 6 series box, it was more or less the same except for a different way to wire up the tachometer. My heavy black ground wire from the msd is going to the negative terminal on the battery. my heavy red is going to a junction box near the battery and the thinner red is wired to the ignition

Oldkckr41 said:

Run a 12 volt jumper wire from the batt. to your coil just to see if it will run.

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I'm on my way to the car in a few, I'll give it a shot and keep you updated