Its about 40 - 50 mins from where I live (Mt Druitt area) It only takes you about 5 - 10 mins from Richmond or if your in Penrith you could probaly get their in about 25 minutes.
Directions
The Richmond Magnetic Hill is located on Bowen Mountain Road in the Township of Mountain Bowen, just east of Richmond. The hill is located at the Mountain Bowen Rd. and Westbury Road intersection. It only works for about 50 metres going uphill.
Directions from Sydney
From Sydney City, Take the Harbour Tunnel or Harbour Bridge, follow the Warringah Expressway straight through to Lane Cove, and follow through onto the M2 Motorway right to the end till the Blacktown Exit - Turn right onto Burns Road which follows onto Old Windsor Road, which runs into Windsor Road, turn right and it will take you right into Windsor. In Winsor make a right turn onto Winsor Richmond Road (40) and it will take you to Richmond. In Richmond 40 becomes Kurrajong Road. After crossing the Hawkesbury River in North Richmond turn left on Grove Vale Road. Then turn left on Bowen Mountain Road. The Magnetic hill is on Mountain Bowen Road as soon as you pass the intersection with Westbury Road
Whereis is your friend click here
I might go back their tonight to show my GF so if I do I will take my camera and try record it im not sure how well it will turn out though as its pitch black around their at night.