I too inherited a 74 280c from my mom and have had it it storage for a few years. Same thing happened. The dealer said that there was a Weber carb conversion kit that solved most of the problems and gave 25% more horsepower. I have since located a supplier that claims to have the kit for $329. The average price being $600. My mom spent $500 to have the Solex rebuilt in Arizona. Before you jump at this, I found that the flap in the air housing was not opening when warmed up so the carb was starving for air. In Arizona someone had removed the 4" hose that warmed the air filter housing. Stupid me wanted everything factory so I put a new hose on so the car was getting hot air, but the flap when it works properly opens for fresh air and closes over the hot air vent. I am selling my car or I would opt for the conversion kit and maybe a mechanical distributor. I have a California car and am wondering how to block all of the tubes to the carb. This is long winded, but feel free to email.