New Engine Won’t Start

Humbly seeking advice and suggestions from you all... '64 273 engine, freshly machined, assembled and back in the car. Got gas, got compression, and have spark. But the spark looks weak at the spark plug. Taught myself the last couple weeks about this ignition system and how to use a voltmeter. Also found a great thread in "Engine Issues" by 69 340 last August which I found very helpful and educational.

I wonder if I have a bad starter. Prior to the rebuild the starter turned the engine over enough and the car would start. (But the engine smoked, thus the rebuild.) Now, I have a new Mopar 24 battery, measuring 12+ volts. With the ignition switched to "ON" I read 11.7V at "+" and "-" at the coil. But when I have someone turn the key to crank the engine, the current at the coil drops: "-" drops to 7V and "+" drops to 3V. At the starter relay, the red wire reads 12V with power "ON", but with the starter engaged, it drops to 9V. Yet somehow, between the relay and the coil "-" it goes from 9V to 7V.

When the motor was out, I painted the engine compartment and the bulkhead was removed. While it was out I used electric contact cleaner before plugging the bulkhead together again.

I measured the coil's primary (1.3 ohms) and secondary (9600 ohms) which are normal (according to an old Haynes Dart 6 cyl manual is have). New points, cond, cap, rotor, Mopar ignition cables. Original point-type distributor, coil, ballast resistor, starter relay, and positive battery cable (negative cable is new).

I bench measured the ignition switch out of the car with a spare battery and was measuring the same voltage coming out that was going in both "ON" and "START" so I figure that's OK.

One conclusion is the starter is old and drawing so much amperage that it sucks up a good portion of the voltage by the time it gets to the starter relay. Then it seems to drop two more volts after that. I figure everything was settled in with the old motor that the engine and the ignition system co-existed nicely. But now with a new tight motor everything is having to work harder and the ignition system is strained.

I have two things left to try: scraping paint off the engine block at the two grounding cables, and cleaning the fuse box (I noticed the fuse contacts are a bit rusty). Perhaps there's a pinched wire somewhere. My last resort is to find a shop willing to correct my mess and get this new motor started. Any help is greatly appreciated.
Author: admin