Because it will suck up mid and high rpm horsepower. The 213 fan is 1.75 inch pitch. It came stock on 68 340’s. It was also used on 383’s and hemi’s I believe. It did not have a fan clutch. The 69 340’s had a 215, 2.25 inch pitch with a fan clutch. It stops driving the fan shortly after idle rpm. Frees up horsepower for spirited driving. It also benefits air conditioning compressors and bigger alternator and power steering. The 216 I believe is the mopar performance fan and I believe it is 2.5 inch pitch. At idle with a fan clutch it will move alot of air and like the 215 frees up power thereafter.
