1971 would see a further relaxation of rules, supercharging of the SV engine was permitted. Supercharged Reliant 750SV units would run alongside the Reliant 0HV 600 engine.

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Taking maximum advantage of these new regulations would be Jerry Evershed, who built the now infamous Warren. Robin Smyth would race the rear engined, supercharged machine, which would be the last SV engined car to win a 750 Formula Championship. Several attempts were made to ban the Warren, which would eventually be permitted to complete the season and winning the championship. 

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At the end of the season the car was sold and two months later Robin Smyth died of cancer. Jerry Evershed went on to build a Mk2 Warren, driven by Rob Wells. The Mk2 would have arguable the most powerful SV engine ever built. Rob Wells stripped the car after it's final race, which later went into Martin Eyre's collection.

1974 would see 750 Formula take on the Reliant 750 OHV engine. David Newman won the 1974 Championship with little competition, now a 750 engine was a must. 

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750 Formula

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In 1977 slicks would be permitted. Wings and aerodynamic parts would be legalised and race cars would grow side-pods.  The Fiat Fire engine would be the Reliant in 2003 and 750 Formula would continue as the world's longest continually running championship. The Goodacre Trophy would continue to be awarded to this day.

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