After you released the hold down nut to allow the tensioner to contact the belt did you rotate the motor (by the lower pulley bolt)at least a few inches to get all the slack on the tensioner side--and then tighten the tensioner nut? Did you spin the tensioner pulley to check for smooth operation (more important than the spring tension--a part I've never had to change on any of the many, many redblocks I've worked on) of the tensioner bearing? Is the tensioner seated to the block square with the pin fully home in the receiving hole? -- Dave