Historical clue formulations

• Prefix with sphere — 2026-09-09
• Powerful auto engine type — 2026-03-13
• Prefix with sphere — 2026-01-03
• Lead-in to sphere — 2024-09-15
• Half: Prefix — 2022-12-04
• Engine type, informally — 2022-04-24
• Muscle car engine — 2019-12-18
• Hot-rod engine, informally — 2019-01-21
• Prefix with cycle or sphere — 2018-12-12
• Powerful engine, informally — 2018-06-14
• Powerful car engine — 2018-03-24
• Powerful engine, for short — 2017-12-17
• Prefix meaning "half" — 2017-07-12
• Half: Prefix — 2016-10-10
• Powerful engine, informally — 2016-08-10
• Prefix with sphere — 2015-01-19
• Half- — 2014-12-28
• ___ engine — 2012-07-12
• Spheric opener? — 2012-05-08
• Prefix with sphere — 2012-02-27
• Certain engine — 2010-09-26
• Prefix with sphere — 2010-02-09
• Prefix with sphere — 2009-12-10
• Prefix with sphere — 2009-07-29
• Powerful auto engine — 2008-12-08
• Hot-rod engine, briefly — 2008-10-14
• Prefix with sphere — 2008-04-09
• Kind of engine — 2007-08-09
• Prefix with sphere — 2006-04-17
• Half: Prefix — 2006-04-05
• Prefix with sphere — 2006-02-14
• Prefix with sphere — 2006-01-09
• Powerful car engine, informally — 2003-10-26
• Half in front? — 2003-08-27
• Half: Prefix — 2003-06-11
• Prefix with sphere — 2003-02-04
• Powerful auto engine — 2002-12-21
• Prefix with 48-Down — 2002-11-05
• Half in front? — 1999-09-24
• Prefix with spherical — 1999-03-23
• Prefix with sphere — 1999-03-14
• Prefix with spherical — 1998-08-13
• Prefix with sphere — 1996-09-24
• Prefix with sphere — 1996-04-04
• Hot-rod engine, for short — 1995-07-13