FWIW, here is some recent info on the subject from the Toronado mailinglist:
There is a heavy duty cooling fan clutch (Delco # 15-4298) which I have been
extremely pleased with. It was used on some of the third series Toros with
factory HD cooling. The front cover is a casting with fins and the overall
length is almost 1" greater than the standard clutch. No problem with the 3
core radiator, but I can envision problems with a 4 core.
I have had great success with this clutch and factory 6 blade (RWD HD
cooling) or 7 blade ('71-'78 Toro) fans and the 3 core radiators in my late
'70s full size cars. The clutch kicks in around 208 degrees on the coolant
temp gage. It also spins the fan at a higher % of the engine speed than the
standard clutches. The RPM based cutout is still reasonable, however, so
the car does not sound like a DC3 taking off like the aftermarket HD
clutches I have tried. Today I had 37 degree air out of the center vents
(Tempmatic A/C still running on R 12) on my '77 403 Delta 88, and the temp
gage never got over 210. This was in 97 - 99 degree weather and in DC
traffic.
There is a heavy duty cooling fan clutch (Delco # 15-4298) which I have been
extremely pleased with. It was used on some of the third series Toros with
factory HD cooling. The front cover is a casting with fins and the overall
length is almost 1" greater than the standard clutch. No problem with the 3
core radiator, but I can envision problems with a 4 core.
I have had great success with this clutch and factory 6 blade (RWD HD
cooling) or 7 blade ('71-'78 Toro) fans and the 3 core radiators in my late
'70s full size cars. The clutch kicks in around 208 degrees on the coolant
temp gage. It also spins the fan at a higher % of the engine speed than the
standard clutches. The RPM based cutout is still reasonable, however, so
the car does not sound like a DC3 taking off like the aftermarket HD
clutches I have tried. Today I had 37 degree air out of the center vents
(Tempmatic A/C still running on R 12) on my '77 403 Delta 88, and the temp
gage never got over 210. This was in 97 - 99 degree weather and in DC
traffic.
