I think I have posted this before at http://www.fordsix.com:

I ran a back-to-back dyno test on a Ford truck modular V8 with a clutch fan disengaged and then fully engaged.
Disengaged it sucked 1.5 HP max.
Engaged it sucked 14 HP max (around 5000 RPM max test speed).

FORD 300 inline six - THE BEST KEPT SECRET IN DRAG RACING!