Different on a '29 than on a '24. On the '29, the levers on the steering wheel control the headlights and the carburetor. Left is headlights, right is carb. The "gas knob" on the dash, I presume is the same as this one, it's just the choke. I believe the timing was advanced or retarded on the '24 models by the lever on the left, up being advanced, down being retarded. I bought this car, the roof is now black and the whitewalls are gone in favor of repro Firestone blackwalls from Mr. Corky Coker here - car is now in Louisiana and we're enjoying it quite a bit - good luck with yours!