Classic/Antique Car Repair: 38 packard starting problem, torque wrench, battery condition

Question
I have a 1938 Packard 6 cylinder with a 6 volt positive ground system. The engine has been completely rebuilt. I can not get the engine to turn over with the 6 volt battery. It will start if I use a 12 volt battery but not the 6. I would like to hook up the generator and voltage regulator but hesitate to do so untill I can get the engine to start on the 6 volt system. The starter seems to be fine when connected to 12 volt but just doesn't have enough strength with the 6 volts. What am I missing......

Answer
Well Earl,he first thing that I would to be sure that the engine is not fitted super tight or that something is not binding. Get a socket on the front pulley nut and turn the engine over with a torque wrench. Is should not take much more than 40 foot pounds of torque to turn the engine over. If that is ok then it is time to check the starter draw and battery condition. With a voltmeter across the battery make sure that there is 6.4 volts when there is no draw. That is the sign of a fully charged battery. If there is not 6.4 volts, charge the battery. Once the battery is charged turn on the lights for a minute or two to remove the surface charge from the battery and check the voltage. If you cannot get 6.4 volts even after charging then the battery needs to be replaced. If you have 6.4 volts crank the engine for 15 seconds. The battery voltage should not drop while cranking below 4.5 volts. If it does the battery or the starter is defective. A battery load test will then be needed. Good luck.
Brad