I didn't see what distributor you are using (OEM or Aftermarket) but having the specs for a typical 216/235 engine may be helpful. My experience has been that greasy 65 year old OEM distributors don't provide full mechanical advance (measured in "engine" degrees) and should be checked and cleaned.
The 216/235 engines have poor combustion chambers for high compression and high RPM. They are low speed, low compression, high torque engines running on poor fuel when new. This combo requires a lot more advance than what we usually think is required. To this point I believe the original specs for 1950-51 235, car or truck, is as follows:
Distributor 1112358 & 1112363
Mechanical Advance (engine degrees)
2° @ 600 RPM
12° @ 1400 RPM
33° @ 3700 RPM
5° initial + 33° mechanical = 38° total when fully wound out at 3700 RPM (not counting vacuum advance)
(Same vintage 216 would be 5°+38°=43° at 3400 RPM)
I would suggest you start there with original 235 initial+mechanical curve. Later tweak for your cam/carb combination from that point.
Paul
