[tremo]

I’ve checked some previous threads under this forum for more details, but didn’t have much luck so I’m tossing this out there…

I have a ’69 Custom S (non-A/C) which originally had a 350ci/2bbl, so it had the stock fan shroud and 4-blade fan with ~1 5/16” spacer.

- Years ago I upgraded to the 19” 5-blade flex fan (Ames P154FK), and it not only helped with cooling on my 400ci, but I also picked up a few 10ths at the track. It was definitely a worthwhile upgrade!

Now I’m looking to upgrade to the 18” 7-blade clutch fan (Ames PF154GA) and heavy duty clutch (Ames P154G) for perhaps better performance and cooling benefits:

- I’m using a 3-row radiator, 50/50 coolant/water mix and a Robert Shaw 160 degree thermostat (recently changed from 190 degree.)
- The 400 runs at ~190 degrees and up to ~210 in traffic on hot 90+ degree days. It does not overheat, but I want to see about having the engine run cooler because I drive it to the track and it gets "heat soaked".
- Current 5-blade fan is half-way in and half-way out of the fan shroud, as it should be for best air flow as per Jim Hand (who also recommends using a thermo clutch fan for best results.)
- For the new 7-blade fan, I would still use the same fan shroud, ditch the spacer and bolt the fan & clutch directly to the water pump as it’s 1 5/8” from flange to fan.

1) Would there be additional cooling benefit with the 7-blade clutch fan vs. the 5-blade flex fan?

2) Is there any evidence of any gains in horsepower and/or torque from going to the clutch fan since there would be less resistance when the fan is not needed at higher speeds?

Thanks for any advice!

Jim.