Air filters or NOT:
Lotus Clubmans' Formula lightweight Seven chassis with Gerrard F3 all steel 998cc BMC Abingdon motor.
Normally aspirated 45DCOE Weber carb.
Turned alloy trumpets.
I bonded, with difficulty, fine copper mesh to trumpet lips, and trimmed.
They were the air filters.
Lotus Formula Ford single seaters (various) 1600cc Ford.
Normally aspirated down draught single venturi Weber.
When leaving the circuit and entering the paddock all drivers drove one handed (right, for gear change) because the other (left) was, with arm contorted over shoulder so hand could be placed on top of carb to prevent stones and grit going down carb intake.
No air filters.
Rally spec Mini Cooper S 1293cc mainly steel Abingdon.
Normally aspirated 45DCOE Weber carb, positioned where speedo in normal mini was, in centre of dashboard.
It was so deafening (impossible for navigating as no intercoms in those days) that a sound proofed box was constructed and fixed over trumpets.
No air filters.
Lotus Seven Series 2 road spec Ford 105E (Anglia) 997cc cooking (standard) motor, Lotus exhaust and manifolds.
Twin inch and a quarter SU carbs.
No trumpets or filters.
Part rally prepared Ford 100E Anglia 1172cc side valve four branch exhaust modified standard carb.
Gutted standard air filter with wire wool loosely packed.
Couldn't afford proper comp filter so bodged it; deluded!
Every other motor since 1971 - factory standard filter; boring!