[Formulajones]

I'm positive they disengage because you can hear the typical fan noise disappear as you accelerate down the road at a normal pace, much like my other clutch fan cars do.

I don't know the pitch of the fans. The Chevelle has it's original 7 blade clutch fan with an added HD clutch, and the one on the GTO was an OEM GM clutch fan that we had in the stash of spare fans, with a new HD clutch on it.

I don't know what you consider optimum but when we have these big engines making pretty respectable HP, and can make them run cool in the Arizona desert heat, it's a win all around in my book

I have no interest in changing it. We made that mistake on dad's GTO thinking there was something better. All that caused was a hot car, found out very quickly the stock setup with an HD clutch and a good radiator not only keeps it more than cool enough, it works better than anything else I tried.