The other day I noticed the harmonic balancer on my wife's car was shot. So this morning I jacked up the front end and removed the harmonic balancer. Went to NAPA bought a new one and installed it. When I went to install my new serpentine belt, it wouldn't fit. On closer inspection of the old harmonic balencer, and a neighbors input, it was concluded that the previous owner had installed an underdrive system. I went to Ford and bought a new OEM pulley for the water pump, so all is well now.
But now I wonder what the purpose of swapping out the pulleys is. There can't be that much of a drag on a 4.6l engine. And on my test drive I felt zero difference in performance.
So is this just snake oil sold to stupid kids?