I have a 1929 Model 666 Durant. A mechanic suggests converting it from a 6 volt system to a 12. Any advice?????

Do You own a car built by Durant? yes

My suggestion is that you keep it original. If all the wiring is right and good, a 6 volt system works. My two cents worth.

Do You own a car built by Durant? 1928 Model 65 4dr

I agree with Mike. Make sure you have big heavy battery cables for the 6 volt system. Ask for them at you auto parts store or farm supply. Also I connect the battery ground directly to one of the starter mounting bolts.

Dave

Use welder cables for leads.

Do You own a car built by Durant? Yes, a 1926 Rugby

what every one is saying is to use double ought,,,or 2zero or "00" sized battery cables and make sure of a cleaned ground contact metal to metal....then 6 volts should be good enough...especially with a rebuilt starter with good clean posts....
12 volt systems use thinner battery cables and do not conduct current well enough for 6 volt systems

Do You own a car built by Durant? 1929 MODEL 70 COUPE & 1930 6-14 SEDAN