Classic/Antique Car Repair: 6 volt battery for 1929 Graham-Paige

Question
Mr. Sears,
I have a 1929 Graham-Paige 625.  I want to put a new battery in it, but I am not at all sure what to get, particularly the appropriate number of Ah.  I know the battery should be a 6 Volt, but that's about it.  The lights on the auto are very dim (inside and outside) and it is very difficult to start.  That may be a function of its having an updraft carburetor (a Carter BB1), but I am not sure.  When I bought the car, the seller told me to pump the gas peddle 10 times before trying to start it.  Now, although I do that, the car will not start. I know that this is a compound question, but if you could help me on each of the parts of it, I will be most appreciative!
Thanks very much in advance!
Steven Lewis

Answer
Good-morning Steve: Sounds like you have a rare nice car. Now to the questions. First before I started replacing parts and throwing money at the car I would want to make a few tests. I would start with testing the battery. Most of the auto parts stores will test your existing battery for you free of charge, or if you have a digital volt ohm meter you can test it your self very easily. The battery rating for you car should be at least 650 CCA (cold cranking amps) and the battery is a 6 volt. These batteries are available at most auto parts stores about 100 dollars. Before having the battery tested make sure that it has been charged as testing a battery with a low charge will often give a false "bad battery" results. If the battery tests OK then check the charging output of the generator. It should read on your digital volt meter 7.4 to 7.8 volts with the engine running at the equivalent of 30 miles per hour. If the voltage is lower then the generator or regulator is defective. Now to the carburetor and starting. The carburetor on your Graham is the same as used on Chevrolets of the period. Parts to rebuild this carburetor are readily available. That said there are several reasons for the long start time. One the accelerator pump in the carburetor could be weak, the float level off, or just plain dirt in the carburetor. There are other reasons like low compression in the engine or resistance across the points in the distributor. So, I would like to see the engine have a compression test, the distributor looked at, and the battery tested and generator output tested. I would also recommend that the carburetor be freshened up. I rebuild carburetors and do a lot of work via the mail. The cost to do your carburetor would be less than $200.