mech fan blade rpm limit?

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Thanks, alot of good info, very true blind. I never thought of that, my wp pulley is larger than the crank. So at 4k the fan is spinning slower than the crank. Im still not sold on the clutch fan. How does it save hp? If it just dis engages at highway speed. If it stays engaged while the engine is warm and under full throttle then whats the point? I also would think that with it engaging and did engaging would put more strain under the water pump and belt

Just thinking here lol. I believe i have a original fan. Build quality should be pretty good right? Although it is old

Are the flex a lite fans a good option at all? They supposedly flatten out at higher rpm

The nylon one is rated to 8,000 rpm, any issue with the nylon warping with heat?
 
Blind Squirrel said:
A 4000rpm limit does not mean a 4000rpm motor limit. You guys are silly sometimes. If your fan is driven at 1 to 1 then I agree 4k is 4k. But most fans are not driven at a 1 to 1 ratio. Do the math guys.

But all fans should be treated with respect. Plastic or metal. Knocking them about can make an ugly shrapnel mess of things quick.
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??? Some of them are even OVERDRIVEN. I don't recall that most old Mopars are what you might call seriously underdriven
 
I need to find a thinner than stock clutch unit for mine. I have about 2.5 inches between the wp and the rad. I have the fixed steel 7 blade on it now
 
It doesn't engage and disengage like a clutch on an air-conditioning compressor, think more of a clutch that is slipping, like engaging and disengaging a centrifugal clutch on a go cart. It doesn't shock the system. But, I would put a blue anodized flex fan in there because all the guys on here that suggested a clutch fan uses less horsepower and makes less noise probably don't know what they're talking about.
 
For a short time I had an aluminum, name-brand , flex-fan. I put it on one spring to see if my 292/508 cammed engine would be any more powerful. Disaster! I made the mistake of bolting it on and heading out to a show, about an hour away. Everything was fine until I slowed down below 30mph.
It wasn't a total write-off day, cuz I had the earlier fan still in the trunk. A short while later,we were on our way again.Lesson learned.
Anybody need a fan?Nearly new,very low mileage, a little dusty; just pay shipping and handling.
 
71DodgeDemon340 said:
Thanks, alot of good info, very true blind. I never thought of that, my wp pulley is larger than the crank. So at 4k the fan is spinning slower than the crank. Im still not sold on the clutch fan. How does it save hp? If it just dis engages at highway speed. If it stays engaged while the engine is warm and under full throttle then whats the point? I also would think that with it engaging and did engaging would put more strain under the water pump and belt
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It will rarely engage at highway speeds.... usually only when you are climbing a long grade at high speed with your foot in it for a couple of minutes. Otherwise, it is slowly free-wheeling. The engagement and disengagement are gradual and take several seconds.. so there is not any sudden strain on anything. It is a real power saver.
 
Another thing to consider is the usage. Fans have a way of stealing minor amounts of horsepower and not always consistently. In the car that I built for the wife's drag/street enjoyment. We will loose just under a tenth when we have to turn the lights on for night racing. A counter to that is - turn the lights on even in the daylight. But a fan can kick in at any point in a run or even not at all. Yes, even clutch fans.
Street only car - the point is mute. Run what you like. Personally I run a dual fan electric on my streeters and a single electric fan on my race. I like the electric's for the space and safety aspects. Hands and fans - nary the two shall meet.
 
Also, those that have problems with cooling more than likely have troubles with shrouding, spacing, and tuning more than anything else. Spending tons of money on the latest and greatest gadget but fail to understand simple fluid dynamics.
 
My cooling system works perfectly just thought that there was improvements to be made on the fan
 
71DodgeDemon340 said:
Heres one rated for 10k. Looks high quality

http://www.manciniracing.com/deheduststfl4.html
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I have used 2 stainless steel flex fans in my day just like these Derales; they looked just as good. The rating may be 10k RPM but the problem is durability. Both of the ones I used eventually had blades start to crack right where the blade comes out from under the riveted clamp. I was fortunate to catch both before they got too far and shed a blade. So, no more stainless blade fans for me.

Nylon plastic bladed fans have worked for me even when racing with engine RPM's to 7500-8000 RPM a LOT (rally, not drag racing so LOTS of extended high RPM operation). I've also had a fiberglass bladed fan last A-OK where the stainless bladed fans failed.
 
Some of yall should really have the Mopar Performance engine and suspension books. They would answer a LOT of these and so many other questions. Not to mention you would have part numbers to go along with those answers.
 
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