Editing Ford 335 engine (section)

==={{vanchor |1972 R-code}} (351 HO)===
The 351C HO "R-code" had a number of changes to help meet emission standards for 1972 compared to the 1971 Boss 351 "R-Code". The camshaft had less duration, but more valve lift, while the mechanical lifters remained unchanged.<ref name="Cleveland"/> The forged pistons were changed to flat-top style and the heads to open chamber heads, but retained the same large ports, valves, and adjustable valve train used in 1971.<ref name="V-8 Data Book"/> This resulted in a compression ratio decreased to 9.2:1 while the cleaner-burning open-chamber heads helped meet the new emissions regulations.<ref name="Cleveland"/> The Ram Air option was no longer available. The engine otherwise remained unchanged from 1971. This engine produced 275&nbsp;hp (205&nbsp;kW) using the more realistic SAE net system and was only available in the 1972 Ford Mustang.<ref name="V-8 Data Book"/> It was, however, now available in any body style or model of the Mustang, unlike the Boss 351.{{citation needed|date=November 2022}} The 3.91 [[Traction Lok]] rear and four speed were still the only available drivetrain.{{citation needed|date=November 2022}}