[68 Firebird]

ok throw my 2 cents in on this topic

My cars setup is as follows.

-11 bolt waterpump with tight clearance to divider plates

-Cold Case aluminum radiator with TH400 cooling lines in use in rad
.
-all factory baffles to direct air into radiator and seal around core support

-original fan shroud my car was born with

-converted to AC pulley for crank and waterpump to speed up water pump and fan

-factory AC 7 blade fan from 76TA using a hayden STD duty fanclutch

-NOS AC Delco 170 degree thermostat. verified to crack open 165 and fully open 180.

-Q-jet 7028276 with proper recalibration done during rebuild and full RA pan setup

-factory HEI with 12 initial 32 total using heavy advance springs for conservative curve.
weird thing is my car idles butter smooth and has more toque off the line with slower
curve. also 12 degrees from VAC ADV and have tried both ported and FMV and neither
effected cooling. but I prefer exhaust note from FMV at idle(today anyway).

-with 3:08 on highway she is happy at 75 and runs just shy of 180 and then drops back down to 170 on backroads. never hear fan clutch engage and happy with cooling.

In my garage for wall art, are the original crank and WP pulleys and 5 blade. they worked
well for years but temp did creep up in traffic. All these changes occurred over 15 years.
biggest bang for my buck was to speed up WP but then factory 5 blade fan was too loud on
highway. thus, installed matching fan clutch and shortly after has to replace leaking radiator and Cold Case was installed. Gas mileage did improve with fan clutch change.

this is just what worked in my car. I have a collection of thermostats that worked and some that were crap. current Delco stat was installed with no additional holes or voodoo.
All original parts were saved if I ever wanted to go back to original setup.

Gerry