GM Full-Size Trucks 1970-1979 Repair Guide

Controlled Combustion System


The CCS system is a combination of systems and calibrations. Many of these are not visible or serviceable, but are designed into the engine. Originally the system was comprised of special carburetion and distributor settings, higher engine operating temperatures and a thermostatically controlled air cleaner. In later years, the thermostatically controller air cleaner was used independently of the other settings on some engines. Likewise, some engines used the special settings without Thermac. In 1970, the TCS system was incorporated and the entire system was renamed CEC in 1971. The name reverted to TCS in 1972. In 1973, EGR was also added to the system.

The various systems, TCS, CEC and EGR are all part of the Controlled Combustion System.


Refer to the TCS, CEC or EGR sections for maintenance and service (if applicable). In addition be sure that the ignition timing, dwell and carburetor settings are correct.