I think that the speed record is for cars using the rc car race people sanctioned (im forgetting the acronymn) parts so I think go cart engines are out. The one that set this record if I recall correctly was build by Associated employers and could have gone much faster if it hadn't crashed into the wall at the track they were racing it on.
....it would put my Kyosho Turbo Ultima (circa 1987ish) to shame.
Eric