mech fan blade rpm limit?

-
BWDart

BWDart

Well-Known Member
Joined
May 25, 2005
Messages
1,382
Reaction score
270
Location
New Braunfels TX
Just put a champion radiator in the Dart and then discovered the fan blade is causing the pulsating vibration (motor vibration thread) looked at some replacement blades and some state 4000 rpm limit should I just go ahead and buy the elec fan/shroud combo for the champion rad?
Thanks
Bruce
 
They will break and send blades through the hood and other places.

If you are going to run up above 5000 rpm get a clutch fan or better yet an electric fan.

BTW a fixed fan will pull up to 25 hp so electric is the way to go.
 
I've used these for many years on high RPM applications...


700x500-uF28jUhO96nDpB7x8204.jpg
 
Hey guys i still have the mechanical fan on my 340. Is there any added benefit to the clutch type? At higher rpm the fan doesnt spin as fast? Also ive seen the flex a lite fans but kinda confused which way to go. Just kinda hate that annoying woosh sound when you rev up with a mecanical fan
 
Any good recommendations? Also how long does the clutch usually last? Is the offset different than a mech fan? Or will it bolt right in place as my old one
 
You have to have a blade made for the clutch has a 2" center to go over the clutch it bolts to the back of clutch all the aftermarket blades I looked at don't work because of 4 little tabs protruding into that 2" hole I got my new clutch at Oriellys oem for Darts w/ac
 
I may have a extra fan & clutch pm me if you need it. You will feel instant difference be tween the two.
 
I have had very good experience with the Ford Truck Thermal clutch and a 7-blade steel fan, running the fan as slow as I could find pulleys for. That 367 sees 7000plus, every time it leaves the yard, and many other times besides.It's been on there for at least 10 or 12 years.I never hear it; Whoosh... maybe it has something to do with the dual 3 inch pipes.
 
flex fans made an audible noise that didnt agree with me. Clutch fans are great, imagine a torque convertor operating the fan, sort of a lazy coupler that gets stiff when heated.
 
AJ/FormS said:
I have had very good experience with the Ford Truck Thermal clutch and a 7-blade steel fan, running the fan as slow as I could find pulleys for. That 367 sees 7000plus, every time it leaves the yard, and many other times besides.It's been on there for at least 10 or 12 years.I never hear it; Whoosh... maybe it has something to do with the dual 3 inch pipes.
Click to expand...

Its not literally a woosh sound but you can deff hear the fan when i rev it up
 
This CAN happen. I still vaguely remember about a 67? or so goat came into the hobby shop one day, and there was a hole in the hood looked EXACTLY like an axe made it ..........except from the inside out.

Asked the owner........yup........Fan came apart and a blade through the hood.

Sometimes when I check "total" advance/ timing, I barely warm the engine, and disconnect the fan belt before checking timing.
 
How does it mount? Is the clutch between the fan and water pump or does it stay on the front of the fan?
 
71DodgeDemon340 said:
Clutch? I dont have a clutch fan
Click to expand...

Well then the whoosh will definitely remind you that the fan is working.
If you do put a thermo clutch on it, the fan will be quiet when the water in the rad is cold.And it will cut out on the hiway,cuz ram air will bring the water temp down below the cut-in temp. If you don't have A/C, it will never respond to that.
In fact, about the only time it cuts in is in traffic. Or on extended idle times.
It's kindof like having an electric fan, but it lasts nearly forever,never has electrical issues, and you never have to think about it.
Until you don't hear the whoosh.
 
But will it stay engaged at higher rpm? If its a thermal clutch how does it correlate with rpm?

Sorry op for getting off topic
 
The thermal clutch responds to air temp, in the vicinity of a bi-metalic strip of metal, curled up in a coil, mounted to the front of the viscous clutch.One end is anchored to the housing, while the other end operates valve inside the unit.As the coil absorbs heat it , closes the valve and engages the clutch which locks the unit up in or near direct-drive,and spins the fan. When the air passing over the unit eventually cools it, the valve opens and the fan coasts. It never really shuts off, the viscous fluid is always driving, to some extent. It can't be much tho, cuz I've stuck a finger into it a time or two;no blood. I wouldn't do it on purpose tho!
-Rpm has no effect on the valve, it's just air-temp coming through the rad, or being pulled through the rad.But rpm does affect the fluid drive. As it rises, the viscous clutch drags the fan along too.And the viscosity of the fluid changes with heat, being much less able to drive the fan when it is cold, and much more able as it heats up.
-So if you leave the line with a hot engine and a hot clutch, engaged, anything can happen along the way to the traps. In could decouple the valve and freewheel at 60ft, 40mph, 80 mph, or not at all.But when it decouples, the viscous fluid will still drive it. And if the unit is then operating in slip mode, it will lag behind anything the crank is doing, which has just got to be kind to the belt. Mine has got many years on it, and many hard miles.
-And from what I have experienced in the shop, when the unit fails, it does so in full lock-up; meaning when you start the engine cold, Whoosh is instant.And the non-thermo's fail by losing their fluid and failing to drive the fan at all.
--I like the Mopar thermo units as they seem to be a lower profile than the Fords,But I have seen many more failed Mopar units,than Fords.
I chose the Ford pick-up unit, on account of the first time I ever heard one kick in. The truck was just idling on the pad, when suddenly;whoosh, the fan kicked in, and hot air began to pour out from underneath the vehicle. No Mopar I had ever come across, operated like that.In my experience,Mopes are a softer start. So after a couple of cycles,I popped the hood and had a look.I saw that it was a bit thicker than a Mope but looked like it would fit on my car. So I motored over to the Ford dealer with my fan and spacer in hand, and sure enough it was a direct bolt-on. I took it home straightaway.Now, some 12 years later, it is still going strong.
 
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.
 
You must log in or register to reply here.
-

Back
Top