Originally Posted by 67Mustang Al.
had an interesting drive home today in the 67. While driving down a gentle slope, after a short run to the supermarket, I lost ignition and coasted to a stop. Hmmmm.With nearly 2000 miles on the new 347 i am puzzled. With the gas tank on a quarter, and power to the coil, i can crank it over ( until i flattened the battery) with plenty of fuel squirting down the barrels and yet not even a fire from any plug. I am thinking the msd may have a problem in it so i will start there i think. I have 12v at the blaster 2 msd coil as well. Any thoughts Dave.
My wife towed me about 2 miles home with her corolla.
It is imperative with MSD to tie the cylinder heads to ground by cable in addition to a block ground. There is so much energy from these systems that the old idea that the head bolts will provide sufficient ground path just doesn't hold any more. Each head needs a clean and dedicated ground path back to the battery. Whether that's directly to the battery or through a chassis connection doesn't matter other than any connection to the chassis needs to be clean and of low impedance (high conductivity); for the most part clean, free of corrosion, oil or grease and dirt pretty well defines a low impedance connection.
Lacking solid (electrically) grounds for the spark plugs; provides enough back EMF (Electromotive Force) by way of the ignition wires to fry the electronics.