360 in 273 Clothing for the ‘66 Valiant.

Jim Kueneman said
The early ones were gigantic... you should see the one on the /6 compressor I got the interior AC stuff from... But they are so smooth with the rubber mounted crank pulley, idler pulleys to keep belt slap to a minimum and that big mass. The '68 Coronet 318 does not even change when you turn on the AC. The '70 and later like on the Duster make all sorts of vibration and rumblings as the dual belts are flapping around.

I have dealer installed Mopar air on my 70 Swinger. Only a single belt on those (a hefty one) and quite a bit of belt buzz at a certain rpm. If I tighten it too much the idler get's noisy and I haven't looked hard enough for a replacement bearing yet. The dang thing will freeze you out with the R12 though.