My '31 has had an overheating problem as long as I've owned it....before and after I converted to 12v and electronic ignition. Its got a C head as well. Had the radiator cleaned/ rodded out. I wondered if timing could be a problem so I installed a timing indicator and marked the flywheel pulley so I could check with a timing light. At low Idle ignition is about 18 degrees ATDC. With higher RPM it goes to about 8 BTDC. Probably not looking in the right places but I cant find anywhere the proper numbers. Appreciate any guidance!