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First of all I'd sort them by chassis type as you have Tjets/Tjet clones, Aurora Magnatraction/AW Magnatraction clones, , Tomy Turbo and one or two Tyco cars at least.

Sort them into those chassis groups and compare them peer to peer as a starter.

This might point out some obvious stuff like 'gravity' cars and various degrees of magnetic assist.

Also try and bring those in each peer group up to the performance of the best in that group in much the same way you would with 1/32.

Clean, oil, new pickups if required, ensure guide pins are straight where metal, axles and wheels run true, no binding parts, etc.

Oh - and that red Dino's nice but the tyres look huge. Are they jammed against the wheel arches or the chassis?