4 blades (stock) or 7 blades, which is quieter?

I just got summit magazine (dont all run to the mail box, read this first) My question is this. Some of you may already know this but my fan really roars like an airplane when it comes on (not my aux fan, my reg. clutch fan) by changing it to a 7 blade new design fan (mine is 4 blades), will it be quiet? I see one by flex-a-lite for 10,000 rmps for serp. belt trucks/cars. Not sure of my diameter though will have to check.

Ron
'89 Suburban/454tbi/2500/4x2

I'm sorry River Burn I don't know about he quietness of a fan, but the way it sound if that fan is that loud it is really robbing the horsepower. I know aftermarket blades straighten out to give you more horsepower at a high rpm. If the blades straighten they can't make alot of noise nor would they move alot of air. I would say the aftermarket fan would be quieter just by thinking that the blades are closer together and the blades do not have as much of a bend to them. I just run an electric fan on my firebird so I do not have a first hand experience with this. I'm just saying what "I" think.

I am thinking the samething, but was asking to see if anyone knew OR like you had an idea. I too think it is robbing HP. The flex fan can bolt up to my clutch fan they say.


Ron

If you would check with Advanced Auto Parts if there is one close. The one here in Louisa Ky sells those flex fans for about 15-20 dollars. I know they will bolt up to a clutch fan because the solid fans are only made for about 4000-5000 rpm then they become dangerous. I've seen new boys put solid fans on those race cars and throw a blade through the hood. Im looking in the new Jegs book and there is a comment about fans. They say to find a fan with a low "pitch" for a quiet operation. The solid fan they say is made for 4200 or less RPM. I was close enough. The fan I see in here that says it has a low pitch is the 1000 series it sells for 21.99 for 17 and 18 inch aluminum and 19.99 for the stainless. It is a Flex-a-lite fan so you can't go wrong here. Good luck


wiley

[raceman6135]

Hey River:

I have an '86 C20 crew cab with the 350 cid engine and factory thermal fan clutch and 4 blade fan, and the only time it "roars" is when I'm spinning the engine over 4000 rpm. Other than that, it's no louder than any other fan I've had on a vehicle.

On my '76 Chevelle, it came equipped from the factory with a 6 blade fibreglass fan, and after it developed cracks, I replaced it with a Flex-a-lite or Derale (can't remember which) 6 blade stainless steel flex fan, and it is as quiet as stock. It is a solidly mounted fan, however, and is still quiet, even at 6500 rpm.

Although this didn't really answer your question, maybe my (and other's) personal experiences will pursuade you to shell out the $20 for the new fan.

Is it possible that some/all of your existing blades are bent? That may account for the increase in noise from it.

I'm wondering, too, if maybe your fan clutch isn't disengaging at higher temps/speeds, and that is creating more noise, too. Did you try replacing your fan clutch? If you've already answered this, sorry for the redundency.

Hope this helps...

DJS

Originally posted by raceman6135
Hey River:

I have an '86 C20 crew cab with the 350 cid engine and factory thermal fan clutch and 4 blade fan, and the only time it "roars" is when I'm spinning the engine over 4000 rpm. Other than that, it's no louder than any other fan I've had on a vehicle.

On my '76 Chevelle, it came equipped from the factory with a 6 blade fibreglass fan, and after it developed cracks, I replaced it with a Flex-a-lite or Derale (can't remember which) 6 blade stainless steel flex fan, and it is as quiet as stock. It is a solidly mounted fan, however, and is still quiet, even at 6500 rpm.

Although this didn't really answer your question, maybe my (and other's) personal experiences will pursuade you to shell out the $20 for the new fan.

Is it possible that some/all of your existing blades are bent? That may account for the increase in noise from it.

I'm wondering, too, if maybe your fan clutch isn't disengaging at higher temps/speeds, and that is creating more noise, too. Did you try replacing your fan clutch? If you've already answered this, sorry for the redundency.

Hope this helps...

DJS

First, I kind of thought maybe they might be bent, as I am the second owner and have found a few things that make me thing he hit something. Like the alt/power sterring bracket had a hair line crack in it. The sway bar was missing and the drivers side bracket to hold sway bar was missing. All these things were fixed. But I am thinking maybe the blades got hit. The suburban looks clean, who knows. I ran it through www.crafax.com and came back clean! Also, keep in mind I have a thm400 (turbo 400 trans) no 4th gear. I estimate the rpm @ 70mph is 2700+ as I have taller tires (32") and changed the rear end (was 3:73;G80) now is a 3:42;G80 I want a flex fan that can handle rpm's about 10,000, as I have seen them, SAFETY I guess. So you found them to be quiet? I have also replaced the fan clutch about 4 months ago. The one on there is a thermo clutch (If I remember) which mean even at high rpm's if it gets hot it comes on, or even at night or on the highway, dont matter. The non-thermo clutch turns off on the highway (high rpms). I have a 180* thermo stat in there, so most of the time (98%) the temp is at 180-190* and the dang thing still comes on! SO you were happy with your flex-fan??

Ron