Quote:
Originally Posted by Fullback66
Are stock Fan pitch 2-1/2"?
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I keep forgetting to pull a 19.5 fan off the shelf to measure depth. Now the strange thing about the manufacturer stating a 2-1/2" pitch is it is ambiguous - "pitch" should be 1 in 1, 1 in 2 or some other number that references drop to distance. I don't think we can us a 2.5:1 pitch because the blades would be nearly horizontal to the water pump shaft centerline, and many of the older trucks that the SD came on had similar fans to the Pontiac AC fan. Maybe we can figure the company wants a total drop of 2.5" from front to rear, and the Pontiac AC fan has that or comes really close.
I can tell you that I have successfully run the severe duty on my original HO 18" fan and many 19.5" fans. Currently have a SD clutch on my GTO, the 2+2, the wagon, and the Bonneville 2DR HT -- and that isn't counting our club cars that run that fan clutch.
Just as well put in an update here on the latest install on the Catalina wagon. It has a new (and still tight) 496ci stroker. It came off the run stand and into the car last month and we are getting some break-in miles on it. Autometer temp gauge was showing between 195 and 200 degrees, but it wouldn't go over that. Figured that's where Hayden had the fan clutch set so I did the fan tweak bending the tip of the coil spring a little farther than normal but figured I test it there. Since then we haven't been able to get the car hotter than the thermostat 160°. Went a little farther than normal on the bend, but summer is coming so will leave it there.