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I had my '37 out last week running around and noticed it was running rough. The Air fuel ratio gauge was showing richer then normal so I figured one of the floats filled with fuel. I pulled the tops off both W-1's and found nothing wrong. Next day I ran over to the fuel station for fresh gas but ran out at the traffic light, luckily it was on a hill so I coasted back down backwards and walked a couple blocks back home. I carried a few gallons back to the truck only to find the battery was weak. I did manage to get it started and went on to the station for fuel and a test drive. It was still running bad. Pulled the battery out and took it to work for testing, 162 cca out of 700, " REPLACE ".

With a new battery the truck is back to running great, A/F is back to where it should be and it fires right off.

Carbking always says, it may not the carburetors fault, and sure enough, he was right. Weak ignition was causing the rich exhaust.

Ok, I’m about to show my ignorance and hopefully someone will teach me something. I have no doubt that you experienced those symptoms and that the symptoms resolved once the battery replaced.

I am, however, struggling to understand HOW the battery replacement resolved those symptoms.

Was the battery so weak that it was pulling power from the generator/alternator and not leaving enough to run the ignition properly? I would just check the output of your charging system to be sure.

I do have a small alternator, but with a bad battery, the alternator couldn't keep up. I also have HEI ignition, it doesn't like lower voltages. The truck would run, just not as good as it should of. The air / fuel gauge showed to much unburned fuel in the exhaust, poor ignition causes that.

Have you checked the charging voltage. Even a small alt. should build up to the charging voltage if not too many asses. are turned on. If the alt. has a shorted diode it will charge some but only about 1/3 of its rated capacity.
George

I’m still struggling to get my head around this.

Ignition issues causing rough running including a rich symptom? Yes, absolutely.

New battery resolving said ignition issues? I guess it happened, but how?

Normally a charging system either generator or alternator will put out enough Amps to power the ignition awhile charging the battery. Watch your volt / amp gauge the next time you start your truck, the charging system should overcome the amp draw to battery it took to start the engine in just a mater of a few seconds. If the battery has a weak or dead cell it will continue to bleed off power and the battery will never become fully charged. So the charging system keeps trying to charge a battery that will not take a full charge.

Now add to this the amount of amperage it takes to power an HEI ignition at full capacity, the charging system just can not produce enough to fully power the ignition while the battery has a constant current draw.

Once an engine is running with a good battery the battery is effectively removed from the system and the generator or alternator provides power to run everything.