A one-litre Formula Three category for four-cylinder carburetted cars, with heavily tuned production engines, was reintroduced in 1964 based on the Formula Junior rules and ran to 1970. These engines (a short-stroke unit based on the Ford Anglia[1] with a special 2-valve Cosworth or Holbay OHV down-draught head, initially pioneered by Brian Hart, being by far the most efficient and popular) tended to rev very highly and were popularly known as "screamers"; F3 races tended to involve large packs of slipstreaming cars. The "screamer" years were dominated by Brabham, Lotus and Tecno, with March beginning in 1970. Early one-litre F3 chassis tended to descend from Formula Junior designs but quickly evolved.
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