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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!!!!
 

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I had a cheap Chinese aluminum radiator that I used to replace the original when it gave up the ghost. Along with that, I had a factory serpentine set up that included a clutch fan with a FAL rigid fan and BB shroud. Car ran at 180 all day long. Bought a fancy new Griffin radiator with dual electric fans when I switched over the MPFI. Car now runs at 185 on a good day and 200+ most others. I am considering going back to the Chinese radiator in the basement as I can't seem to figure out why it would gain 20+ degrees other than the fan not pushing air through the radiator most of the time.
 

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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!!!!
Do you think this is better than the original air conditioned Big block 1970 Chevelle GM 7 blade fan with a heavy duty clutch fan ? This cools my air conditioned Chevelle very well in 100 deg. weather.
 
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It is great that you resolved the issue. Trust Cadillac for the goods. Flex fans always scare me a little. With flex comes eventual fatigue, plus they spin at full r.p.m. I like the idea of a clutch fan with lotsa blades.The factory K02 fan in '66 was a 17.6" 5-blade affair with a viscous clutch. Around the seventies they used 7 staggered blades, a good choice for function.
 

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Discussion Starter #7
I looked closer at the Cad. fan blade. It is about 17.5 inches diameter and is 3.5 inches tall on a table. I removed the engine and fan from a 73 Eldorado with less than 40,000 miles and the fan has been in my shop for 20 years. I inspected it real closely before I tried it. Yesterday I was in town, stop and go traffic, close to 90 degrees, the engine got up to 200* but I could drive 2 blocks at 20 mph and the temp gauge would start dropping. I will not be putting that 4 blade fan back on very soon.
 
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