By 1970 the 390 V8 FE engine was becoming outdated. With pending emission requirements, a more modern replacement was needed. Although the big-block 385 family was used to replace the larger displacement 428 V8 FE engine, this engine family had nothing comparable in size to the 390 V8. For the 1971 model year, Ford introduced the 400 V8 engine as a replacement for the 390 V8. Ford billed the 400 as the 351C's big brother. It was designed to provide brisk acceleration in medium to heavy weight vehicles in an engine package that was smaller and lighter than the FE V8 Engines and the 385 Series Ford V8's.