How much room must I give a cyclist in a 8 foot lane?

cyclist is a vehicle and is entitiled to the full width of a lane, just like a car

MTO recommends giving them 1 metre of space to your right, and if the cyclist is riding defensively, they will also be leaving themselves about 1 metre to the curb. If you can't give them that space then you should signal and change to the next lane to pass.

most lanes are 3.5-3.75m wide....bicycle should be out about 1 metre (or in right tire track) to avoid drains, gutters etc...

this will leave 2.5-2.75m.

Add in the width of a bicycle 50cm... now down to about 2.0-2.5m of room.

Add in 1 metre for clearance....now at 1.0-1.5m of room.

Smart Car 1.51m wide

Honda civic 1.71m wide

Toyota Highlander 1.83m wide

Crown Vic 1.98m wide

without going into another lane.....it is even a tight squeeze for a "Smart Car"

A lot of streets up here have no curb, so I can incorporate the gravel shoulder into the defensive 1 metre to my right. On those streets I will ride about 15 cm from the solid white line and cars have just enough room to pass me by driving to the left edge of the lane. Near a crest of a steep hill on a two-lane road I will move out and take up the entire lane to prevent cars from straying into oncoming lanes.

In downtown areas you will likely never be able to pass a cyclist properly unless you switch lanes or they have a bike lane. In Toronto though, I have noticed that there is almost an unspoken rule that cars in the left lane will shift over, allowing cars in the right lane to straddle both lanes for a bit and pass the cyclist safely. It would be a bad idea to assume this space will always open up, though.