Classic/Antique Car Repair: 1952 Packard wont start when engine hot, engine cold, auto stores

Question
Hi Brad. I've purchased a 1952 Packard for my father as a surprise but I haven't been able to give it to him yet. While it runs great at first, the car won't start after it's been driven for 30 minutes and gets hot. You have to wait an hour for it to cool down. The first mechanic claimed it was a bad starter and sent it out to be rebuilt. The rebuilt starter didn't resolve the problem. The second mechanic insists that the first mecahnic didn't rebuild the starter properly, but we want to exhaust other possibilities before looking at the starter again. I've read on line that coils could be overheating or that the starter needs a heat shield. Any ideas? Thanks in advance for your advice.

Answer
Well it is time to stop guessing and do a little testing. A simple volt meter, around 20 bucks at most auto stores, will get you some good test results. With the engine cold remove one of the small wires from the coil so that the ignition is dead. Connect the voltmeter to the battery with the scale set on 20 volts DC. Crank the engine over and listen to the sound of the starter, observe how fast it is cranking and read the voltmeter while it is cranking. Write down your results. The voltage cranking should be more than 4.3 volts. If it below that then there is either a battery problem of a deft in the starter. If all is well, reconnect the coil and run the engine for the 30 minutes. Then retest and record your results. If the voltage is below the 4.3 volts, then the starter is suspect. If the starter appears to be laboring and the speed is not what it was cold, there could be heat related problems in the engine. If the coil is defective the engine will crank normally and the voltage will be higher than 4.3 but the engine will not fire. Remove the coil lead from the center of the distributor cap. hold the wire by its insulation so that the connect or that was in the cap is about 1/4 inch from a good ground. Have some one crank the engine with the key on and watch for a spark. It should be bright blue. If you have spark it is not the coil. Try these steps and let me know the results and we will go from there.