Editing Ford 335 engine (section)

===Replacement===
The 351M and 400 were last offered in a Ford passenger car in 1979. They remained available in Ford light-trucks until 1982. Reduced demand for larger engines due to tightening [[Corporate Average Fuel Economy|CAFE]] regulations led to the abandonment of the 351M/400 and the Cleveland production line. By 1980, mid-sized V8's had disappeared from the option list for almost all Ford cars. Only the full-size [[Ford Panther platform|Panther]] platform Fords had anything larger than 302 ci available, and this need was filled with the 351W. With low demand for engines in the size range of the 351M/400, the 335-series V8's no longer had a need to be produced.

In addition, there were difficulties adapting the M-block to the second generation of emissions controls. Unlike previous Ford engines, [[Thermactor]] and [[exhaust gas recirculation]] features had already been built into the 351M and 400 engine, rendering adaptation to electronic feedback fuel/air systems difficult.<ref name="bubba demise">{{cite web|last=Resch|first=Dave|title=Demise of the M-Block|url=http://grantorinosport.org/BubbaF250/history/history04.html|access-date=22 May 2014}}</ref> One requirement of the second-generation equipment was an oxygen (O<sub>2</sub>) sensor in the exhaust, which had to be placed before the Thermactor air was added. Since Thermactor air was injected right into the block's exhaust ports in the M-block, there was nowhere for the O<sub>2</sub> sensor to go.