My mag does not work and I have drove all summer on battery,seems to run good except it will do a quick miss at high rpm,s how much damage will it cause if I change the voltage regulator and run 12volt
John
Here is a link to an article that explains why this high speed missing occurs.
More on Model T Spark Timing
No damage will occur using 12 volts with the coils if you are CAREFUL.
You cannot let a coil buzz continually for a long period of time without the engine running or you can look forward to this.
You might want to try an in the car magneto recharge. In your situation it is a good last chance try to revive your magneto.
Ron the Coilman
I have already tried a recharge with no luck, but will running 12 volt make any difference in performance?
John
Yes, certainly. Read the article and you will understand why.
Ron the Coilman
John, If you get bored? pull the starter and look at the coils around where the starter goes through, more than likely some one has tried to pull the bendix through that hole and ruined the fields!