drove my 71 chev pu for the first time this summer,it was about 88 degrees out. The engine is a 402 bb with engine & trans cooler.with the 3650 cfm zirgo fan it started off getting hotter than normal,usually runs 180 ran 210 on the highway 220-230 in town .I have a manual switch & thermastaticaly controlled switch.I put the old clutch fan back on , ran it on a 105 degree day , it ran 180 on the highway 190 in town. Just thought i would pass this along to any unsuspecting buyers ,not to make the same $ 400.00 mistake.