Take the valve cover off and look at the rocker arms on #6 cylinder. As the exhaust closes and the intake begins to open, #1 will be coming up toward TDC on the compression stroke. Cylinders reach TDC in pairs, 1&6, 2&5, and 3&4. They're just 360 degrees apart in the 4-stroke cycle, one on top of the exhaust stroke, and the other one on TDC of the compression stroke. It's also an excellent way to find TDC for valve adjustment.
Jerry