The final model of the above initial series was the "MAE" in 1965, when new rules were introduced in Formula 3 allowing up to engines with 36 mm intake restrictor plates. MAE used one barrel of a two barrel Weber IDA downdraft carburettor with the other barrel blanked off. The domination of this engine was absolute as long as these regulations lasted until 1968. As Cosworth had a serious difficulty meeting the demand, the MAE was mainly sold as a kit. This experience led to the later FVA/DFV contract to be drawn where the responsibility of development rested with Cosworth, and the manufacturing right and responsibility rested with Ford. There also were some specially cast iron heads with similar dimensions to these brazed heads with titanium alloy valve spring retainers called the "screamer head" for MAE in later years.