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I'm using the original 4-blade fan, no clutch, on my '60. There's a significant amount of noise from the fan, as a result.
Does anyone have any recommendations for a quieter fan? I was thinking about using one of those Flex-lite offset 7-blade fans, or maybe just getting a fan clutch and using the GM offset 5-blade fan that was an option for '60.
Adding a fan clutch is the best solution! With a rigid mount (standard through 1960), the engine is trying to 'fly' at high RPM. Not only will high RPM operation quiet down, but you'll get a minor boost in HP to boot with a fan clutch. That's one of the reasons it became a standard feature in 1961...
Good point. I already have an original offset 5-blade fan, I was just hoping to avoid using a repro fan clutch, due to the expense (a new 'universal' fan and new 'universal' fan clutch appear to be cheaper than just a repro fan clutch)! I'll take it into consideration.
Back in the 60's, Ford used to sell clutch fan kits OTC as a performance upgrade, claiming 2% hp increase. My '97 SUV has a thermal clutch fan, most likely to improve fuel economy, another benefit. The clutch fan is much quieter at speed and during acceleration, since even when engaged it runs slower than crank rpm. When idling, it is very quiet.
I should have added, that when the thermal clutch is not engaged, it is very quiet as well. This is an important distinction to make, as there are many non-thermal clutches available, basically all they do is act as a viscous mount for the fan, reducing the speed of the blade at all times, regardless of need. The thermal type, on the other hand, senses the temperature of the air coming through the radiator, and speed up or slows down the fan as needed by the cooling system.These are much better than the non-thermal type. You can stand next to your car on a warm day and actually hear the change in the fan pitch as the engine idles. when the car is moving, chances are the clutch will never engage, since plenty of air is moving through the radiator.
It's not just temperature that controls the fan clutch. Factory specs called for %-slip (the difference between input shaft RPM and output rotation expressed as a percentage) to vary with BOTH ambient temperature and input RPM. It's a rather complex 3-D relationship....
If memory serves, the net impact of the fan clutch back at it's Corvette debut in 1960 was to boost power by roughly 10 HP. If you compare the selling price of the fan clutch option ($21.55) to the difference between similar engine power plant differentials, this was BARGAIN in performance!
But, Corvette wasn't the first Chevy vehicle to offer the technology. It went back as far as 1958 on certain full size Chevy cars...
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