Cooling Fan speed?

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512Stroker

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18 inch, 7 blade factory Mopar cooling fan
Direct belt driven, no clutch
Crank pulley - 7 1/4 inch diameter
Water pump pulley - 5 1/4 inch diameter
What engine rpm can I safely run this fan setup ?
 
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Till the fan comes apart.

Not being a ****. I just have not seen any speed ratings on oem fans.

As is you are overdriving the fan by about 40%. So if engine is 5000 RPM fan is around 7000 RPM.

On my stock 273 the fan and crank are much closer to 1 to 1(IIRC)

Typically in a racing setup the fan and alt pullys are larger in diameter than the crank pulley to underdrive them
 
18 inch, 7 blade factory Mopar cooling fan
Direct belt driven, no clutch
Crank pulley - 7 1/4 inch diameter
Water pump pulley - 5 1/4 inch diameter
What engine rpm can I safely run this fan setup ?
18 inch, 7 blade factory Mopar cooling fan
Direct belt driven, no clutch
Crank pulley - 7 1/4 inch diameter
Water pump pulley - 5 1/4 inch diameter
What engine rpm can I safely run this fan setup ?
i am having cooling issues at low speeds/idle and am looking for a 5” water pump pulley. Where did you get a 51/4” pulley?
The shop manual for my 71 318 and a/c calls for a fan to crankshaft pulley ratio of 1.3:1. My current set up gives me a .92:1. I want to leave the crankshaft pulley alone so as not to speed up alternator.
Thanks a ton.
 
i am having cooling issues at low speeds/idle and am looking for a 5” water pump pulley. Where did you get a 51/4” pulley?
The shop manual for my 71 318 and a/c calls for a fan to crankshaft pulley ratio of 1.3:1. My current set up gives me a .92:1. I want to leave the crankshaft pulley alone so as not to speed up alternator.
Thanks a ton.
That was on a BBM.
I think that was a March water pump pulley and a factory crank pulley for an A/C car. You will find that the factory A/C cars had the over drive ratio's.
 
i am having cooling issues at low speeds/idle and am looking for a 5” water pump pulley. Where did you get a 51/4” pulley?
The shop manual for my 71 318 and a/c calls for a fan to crankshaft pulley ratio of 1.3:1. My current set up gives me a .92:1. I want to leave the crankshaft pulley alone so as not to speed up alternator.
Thanks a ton.
The alternator speed is not an issue. In fact they perform better at higher speeds. So let her rip
 
18 inch, 7 blade factory Mopar cooling fan
Direct belt driven, no clutch
Crank pulley - 7 1/4 inch diameter
Water pump pulley - 5 1/4 inch diameter
What engine rpm can I safely run this fan setup ?
Pretty sure it has to do with how the blades are attached to the center. If all the rivets are tight and pass a visual inspection I wouldn’t be worried at all. The aftermarket rigid “race” 6-blades such as from Derale, Flex-A-Lite aluminum and steel versions are rated to 8000 rpm and that’s not blade rpm, it’s engine rpm. I know Derales have 5 rivets per blade. How many rivets per blade on the Chrysler 7 blade? That’s all I’d be focused on. Tight rivets with no signs of rust around them and run it.
 
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The aftermarket rigid “race” 6-blades such as from Derale, Flex-A-Lite aluminum and steel versions are rated to 8000 rpm and that’s not blade rpm, it’s engine rpm.

Are you sure about that? It seems weird that a fan manufacturer would rate a fan based on engine rpm when fan rpm ultimately depends on pulley ratio.
 
Are you sure about that? It seems weird that a fan manufacturer would rate a fan based on engine rpm when fan rpm ultimately depends on pulley ratio.
Ok you got me on that technicality. Depends on the pulleys being used. I’m using CVF pulleys and the water pump pulley is 6.4” and their crank pulley I have is 6.4” (which is their high flow size, they have a smaller diameter under driven type crank pulley also) so when I rev’d my engine to say, 6400 rpm the Derale mechanical 6-blade spun to??? Yes, 6400 or as I said , engine rpm. I should have been more specific :)
 
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