This graph show the viscous clutch on the original Mopar 340 V8
Doubtful, the 340 isn't a 5.7L. More likely it's a SBC.
No, I have read those two footnotes and the fan/viscous data is from a Society of Automotive Engineers (SAE) on the then new 340 V8. Some of the generator shaded area in the graph showing variation is from a SBC 350
