The 351 Cleveland began production in July 1969 1969 for the 1970 model year. Its actual displacement was . A 4V (four venturi) performance version and a conventional 2V (two venturi) version were built. The 351C-4V was marketed as a high-performance engine, featuring the 4V large ports heads with closed "quench" combustion chambers. Later versions of the 351C with 4V heads continued to use the large ports and valves, but switched to open chamber heads in an effort to reduce engine emissions. The 351C-2V was never marketed as a high-performance engine. It used the small port 2V cylinder heads with open combustion chambers to produce a more economical engine that was tuned more for low-rpm torque. Only the Q-code 351 "Cobra Jet" (1971–1974), R-code "Boss" 351 (1971), and R-code 351 "HO" (1972) versions have four-bolt main bearing caps, however, all 335 series engines could be modified to have 4-bolt main bearing caps.