when setting the 190e 8v to tdc, the "o" mark on the balancer is tdc of the crank, on the cam, look behind the gear, there is a small notch cast into the cam this must align with the valve cover surface of the head on the drivers side of the engine. If the cam timing has been altered it will effect the way the engine runs. a reterded setting will give poor bottom end but will extend the top end range the engine will rev.
hope this helps.
Joe