[geeteeohguy]

Originally Posted by Schurkey

Good, not great.

A shroud on the fan would make it far more efficient, which means you wouldn't need the "extreme-duty" fan clutch with a modified spring--or the horsepower to drive it.

The Heavy- and Severe-duty fan clutches are not suitable for use with typical automotive fans, (Less than 2 1/2" of pitch) because they'll never properly disengage. Hayden says as much on their web site.
http://www.haydenauto.com/Featured%2...s/Content.aspx

How much engine vacuum do you have at highway cruising speed?



That's all the evidence I need to know that either your cooling system doesn't have the heat-rejection capacity it should, or there's problems with excess heat generation.

210 is 40 degrees over the nominal 'stat temperature. The 'stat lost control of the temperature at 20 degrees over. The cooling system is running wide-open and has zero capacity for additional load.

Nonsense. These numbers apply to the 9 GTO's I've owned and others I've driven over the past several decades. I have put 100's of thousands of miles on these cars without issue at temps of 200-215 degrees. New cars RUN at 220-240 as a norm. Not one of my GTO's would run 180-190 degrees on a 110 degree day at 75-80mph for hours at a time. My experience, no matter what GTO I drive, is that they will run OVER thermostat temp on VERY HOT DAYS, period. And this experience is with MANY GTO's, not a single car with a suspect cooling system.