The Stovebolt Site Forums The Shop Area Engine Shop 54' Chevy Starting Issues, Not even a whir

Voltage isn't what matters with a starter. Amperage is. You can have a good solid 6V to the starter, and it still won't crank because there's not enough capacity to transfer energy to the starter. Starters require a ton of amperage. 6V systems require double the amperage of 12V systems and the amount of amperage will vary based on ambient temperature and the amount of friction in the engine that has to be overcome to turn it over.

The positive cable looks rather small for a 6V system. It should be at least 00 gauge. Furthermore, a poor connection on the ground side can affect the ability for current to pass through the system as well. Just because the braided cable is attached to the frame doesn't mean you have a good ground. You should sand the frame and the connector and clean up the bolts that mount the braided cable to the frame of the truck as well as the case of the starter. (If that's what you mean by "cleaned up all the grounds", then please don't take offense to my advice.) And don't forget the ground connection for the battery itself. That can often be the culprit.

Since the last two times that it started where when you "hooked directly to the starter", that's an indication that one of the connections isn't sufficient to turn the motor over.