My outfit (312) runs 100°-105°F over ambient - with this temp taken at the thermostat housing. So summer day at 105° ambient - the housing is 210° - and winter (Arizona) the temp goes down to the thermostat setting (160°F) and hangs there. These temps are taken from a long static idle (burn down) test. I'd like to get the range narrowed down so the idle tune is a bit more constant - so I gathered up this set of parts...

A high flow, 180°F, Mr. Gasket thermostat (big block Chrysler size) with three added 3/16 bypass holes drilled in the nose.

Single groove pulley from a '69 302 motor, aluminum spacer to accomodate the deeper nose, and a brass plug to shut off the bypass hose - so all of the water flow has to go through the thermostat / radiator.

The spacer is 1.0" thick with a long enough nose to engage the (six blade) fan bore directly - fan mount is right on the pulley face. The smaller diameter pulley should net about 20% overdrive (relative to the original pulley). The closed off bypass may not be good for Michigan warm-ups - but my engineer's brain keeps telling me it ain't a good idea to have a 5/8 hose bypassing the radiator on a 105° day. 

I'm sure others have others must have tried this before - does it work? This is for a driver car - belts loose at the track.

 
 Steve Metzger       Tucson, Arizona