Trouble setting timing

[Stripes]

I've been trying to get my timing on point today and I'm having a problem.

I set the crank 2nd tooth from the left (#1 tdc) and I have the chain properly lined up with the cams. Everything is fine and set until I put the chain tensioner in. If the crank is set at #1 tdc, once I put the tensioner in it pulls the slack and turns the crank ~20 degrees clockwise so the cams are still where they were but now the crank is not set at #1 tdc.How can I get the slack to the intake side before putting in the tensioner so that when I do put it in it will not turn the crank?