My 66 chevelle, 396, 360 HP, powerglide, 4 blade fan, factory shroud and original radiator ran 190 degrees on the open road on a 90 degree day. But town driving, stop and go would get it up to 230 even with putting it in neutral at the lights and increasing the idle speed. I hit a deer last winter which required a new radiator. Installed a Cold Case, the two core, what a beautiful item. Replaced the fan shroud also and used the factory four blade fan. When it finally warmed up around here after the 4th of July, the same cooling issues returned. I have a complete 500 CI 73 Cad motor with a fan that looked like it belongs on a dozer. So I decided to give it a try. I used my Chevelle fan spacer, the center guide fit perfect, but I had to file out the 4 bolt holes a little. In place the Cad fan clears the harmonic balancer by 1/2 inch, protrudes out of the fan shroud about half way. With the hood open and I started the motor I could feel a lot more air movement. Yesterday took it into town and it was around 90 degrees, stop and go driving saw about 200 degrees and when you rev up engine the temperature drops pretty fast. The fan is a GM part # 1370318B. This is a big flex fan and when you rev the engine you can see the blades flex, but at an idle they are 3 inches deep. They move air!!!!