There is, last night I was inside at the connaught grandstands and was walking past MArina Square, they still did not restrict access from that lobang at the stairs of Marina Sq, location is situated between the Raffles One Link <-> Marina Sq bridge and the 2nd sty food court. Got flight of stairs there. I don't know how to describe, but very clear. Distance = about 50m.
You won't get closeup shots, some regular somewhat wide shots prob. Shoot Porsche also ok what (this year no Aston Martin), coz daylight + the track lights shd be easier to shoot.
Technically can shoot closeups, there are refractor telescopes which you can use on dSLR, just fix focus on the track. Astrographs, some have optical quality which are much better than primes. Fancy a 8000mm f10? Can even catch the eyelashes of a babe at that distance. LOL!
Don't really need AF or metering actually so its gonna be FAST. ISO 1600 daylight, cool even for f10 operation. Just that the "lenses", tripod and mount would be so big that it would make a 600 f4 + photo gimbal look like toys.
Anyway, enjoy.