I have been working on this 1947 B late model for the past eight months. When I first got the tractor, the engine was stuck and the gear shifter would not move. I have been able to get the engine freed up and also the gear shift. I flushed the engine and installed new oil filter and oil. I installed 12V alternator, points, condenser and coil. I have installed new Marvel Schrebler carb and pulled the valve cover to check condition of valves and springs. We have tried starting the tractor and it tries to start, but backfires. I pulled the flywheel off while working to free up the shifter and reinstalled it as it was. We have not moved the distributor. Can the distributor be rotated to change the timing, like a car distributor?