Just a 40mm fan mounted behind the motor blowing air onto the motor with a gap of 5-10mm. I use Ride servo tape to stick the fan down to the chassis as it's really strong. Heat sinks are not needed with today's brushless motors.
Serpent Viper 977e, Serpent 748e, Serpent 811T-TE Truggy, Serpent 811e 2.1, Serpent 411 4.0 Eryx, Serpent SRX-2 RM, Serpent SRX-4, Serpent F110-SF2, Serpent F180, Serpent 748 Natrix WC, Serpent Cobra GT 3.0, Serpent SRX8, Serpent S811 2.2, Baja 5B Flux, Atomic AMZ 1/27th, Schumacher GT12 SS.
Sanwa, Ielasi Tuned Novarossi Racing Engines, Tekin, Hobbywing, Muchmore.