It's a conventional thread, the fan is a nut, the shaft is threaded. I used a bit of pipe with pin jammed into one of the holes on the hub to hold it still and a large spanner on the nut, it took some persuasion to get it off, in the end I used freezer spray on the nut and hit the spanner with a copper mallet.
Standing in front of the engine you need to rotate the nut (fan assembly) to the left.
It's a chore so I'd do it as part of the cam service if it was my car. If you are in Europe (maybe thd US too?? I see its made in Canada) the SKF have an eBay shop selling the full cam kit, I have one on the shelf to do on mine in the spring.
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