Excessive Fan Noise due to fan speed

[68 Sport Satellite]

How many of you have experienced excessive fan noise due to fan speed and what did you do about it?

I recently had help from KD swapping engine pulleys and brackets as part of a Vintage A/C retrofit. I've been running a stock 1968 OEM 18" fixed steel fan. When the water pump pulley was swapped from non-A/C type to the smaller A/C type, the fan speed increased as expected. What I wasn't prepared for when doing the first time test drive, is that when I romped on the Go pedal, the fan noise caused by the large increase in wind air velocity sounded like a jet plane taking off. It's a pretty loud whirring sound. After warming up the motor, driving for 20 min, then letting it idle for 5 min, the coolant temp at idle shows a marked improvement idling around 175-180F instead of the previous 195-210F. While this is great, I don't think I can drive the car like this all the time with all that extra noise.

Have any of you experienced this with a smaller pulley setup? I know I know - install louder exhaust! Turn up the radio!
KD suggested installing a thermal clutch fan (which I have, but haven't tried yet). I've got a re-pop 18" diameter steel 7-blade clutch fan from Bouchillon (although wondering if this fan metallurgy could suffer from similar self-destruct issues like the re-pop steel pulleys I've seen come apart, which is the reason in my pulley swap I used original steel pulleys instead of repops). To go with the fan I've got a Hayden thermal clutch. I know the basic premise of a clutch fan where at speed it will slow the fan down, but I'd like to hear from others who had high speed fan noise and if a clutch fan solved the issue?

 

[copper67sat]

M '67 is an original AC car with a clutch fan and I had this same noise when the fan clutch went bad and locked up. I have had this happen on newer (2000-ish) cars as well and it was always a bad clutch. Sounds like you are not running a clutch so likely source is excess fan speed with the smaller pulley.

 

[1967coronet]

When that 7 blade mopar fan is moving air and my thermoquad is wide open it's music to my ears.

If it's to loud though I bet your clutch fan set up will cure the problem.

 

[68BabyBlue]

I can't speak to the small pulley issue, but the '69 GTX with factory A/C I owned in the 90s had a fixed factory fan installed for maximum cooling. Car was a daily driver in Virginia with original owner. At cruising speed the fan noise was noticeable. My current '69, also a factory A/C car, has the reproduction thermal fan clutch from Tony's Parts installed. It's silent at road speed, and since I had the radiator re-cored, runs almost as cool as my former car with the fixed fan. Back in 1970, when I drove that same GTX for the first time, I was amazed at how quiet it was under the hood compared to my dad's slant six Valiant with a fixed blade fan.

 

[Ron H]

Hmm, haven’t heard of this, I switched my 4-blade to 7 and installed an OEM shroud on a hunt to lower engine temp. Didn’t add a clutch or change pully size. As mentioned could be the increased spin. My motor has solid lifters that generate a lot of noise; but no heady fan noise that I’m aware of. Maybe a clutch would be a fix or insulating the hood as I’ve been thinking of doing.

 

[not so famous bob]

How many of you have experienced excessive fan noise due to fan speed and what did you do about it?

I recently had help from KD swapping engine pulleys and brackets as part of a Vintage A/C retrofit. I've been running a stock 1968 OEM 18" fixed steel fan. When the water pump pulley was swapped from non-A/C type to the smaller A/C type, the fan speed increased as expected. What I wasn't prepared for when doing the first time test drive, is that when I romped on the Go pedal, the fan noise caused by the large increase in wind air velocity sounded like a jet plane taking off. It's a pretty loud whirring sound. After warming up the motor, driving for 20 min, then letting it idle for 5 min, the coolant temp at idle shows a marked improvement idling around 175-180F instead of the previous 195-210F. While this is great, I don't think I can drive the car like this all the time with all that extra noise.

Have any of you experienced this with a smaller pulley setup? I know I know - install louder exhaust! Turn up the radio!
KD suggested installing a thermal clutch fan (which I have, but haven't tried yet). I've got a re-pop 18" diameter steel 7-blade clutch fan from Bouchillon (although wondering if this fan metallurgy could suffer from similar self-destruct issues like the re-pop steel pulleys I've seen come apart, which is the reason in my pulley swap I used original steel pulleys instead of repops). To go with the fan I've got a Hayden thermal clutch. I know the basic premise of a clutch fan where at speed it will slow the fan down, but I'd like to hear from others who had high speed fan noise and if a clutch fan solved the issue?

my opinion , run a clutch type fan , biggest one you can get in there , and at least stock pulleys , no small pulleys !!

 

[Gus chiggins]

my opinion , run a clutch type fan , biggest one you can get in there , and at least stock pulleys , no small pulleys !!

Yep, 1:1 pulleys. No underdrive

 

[68 Sport Satellite]

my opinion , run a clutch type fan , biggest one you can get in there , and at least stock pulleys , no small pulleys !!

yep, I have stock pulleys, but they're now OEM junkyard for an A/C car since my car was originally non-A/C and is now getting a Vintage Air A/C setup installed.

 

[68 Sport Satellite]

Sounds like the consensus is to run the clutch fan setup.
I'm good with the new Hayden thermal clutch I have.

Have any of you run the re-pop 7 blade 18" fan from Bouchillon? Is this one recommended?

 

[Photon440]

Funny, I just (on Tuesday) read an old Mopar Action where Rick Ehrenberg explained how much quieter the engine compartment was with a fan clutch, and with reduced cavitation it could also improve cooling at high rpms.

 

[1KoolBee]

Just put a factory a/c clutch fan on it with hopefully a factory clutch, 7 blade, 3” pitch. Direct driving a fixed or flex fan at high speeds is a recipe for disaster. I once had a stainless flex fan on my bee, made some scary noises at 6000 rpm’s, didn’t cool any better than the factory setup. Fan does nothing for cooling above 30-35 miles an hour anyway.

 

[Dave6T4]

I run one of those factory flex fans found on '80's 5th. Ave's. At speed, they flatten out and are not noisy. At idle or slow around-town speeds, they curl, and really pull the air through the radiator. I have had little luck with clutch fans over the years.

 

[68 Sport Satellite]

Just put a factory a/c clutch fan on it with hopefully a factory clutch, 7 blade, 3” pitch. Direct driving a fixed or flex fan at high speeds is a recipe for disaster. I once had a stainless flex fan on my bee, made some scary noises at 6000 rpm’s, didn’t cool any better than the factory setup. Fan does nothing for cooling above 30-35 miles an hour anyway.

I don't have a flex fan and never plan to run one.
I've been running a factory 7-blade steel fixed fan for 6K miles with 20 drag race passes and many highway miles and no issues.
My radiator is not factory - it's a 26" Griffin aluminum exact fit, but is a bit thicker than stock. Now that I've swapped to the smaller A/C pulley, the fan spins faster and is very loud. So I've decided to swap to the 18" steel 7-blade clutch fan. I have 2 new Hayden fan clutches, one stock neck and one short neck to see which fits better.

 

[68 Sport Satellite]

KD has been helping me with the clutch fan install to replace the fixed fan since I hired him to do my A/C install. He reports back that with my new Hayden 2947 shortie fan clutch and steel clutch fan, the fan noise is LOUDER with the clutch fan than with the previous steel fixed fan. That is the opposite result I was hoping for since some on here have reported that installing a clutch fan setup with the smaller A/C pulley reduced fan noise.

Has anyone ever had a new fan clutch that's too tight, but later breaks in and loosens up a bit? Is there any correlation between clutch neck height being shorter and increased fan clutch tightness?

With the smaller A/C pulley, both the fixed fan and clutch fan are too loud. No electric fans for me. What are the options?

 

[Bird 426]

I have clutch fans on all 3 of my cars, I can not hear the fan on any of them. Something doesn't make sense.

 

[Kern Dog]

Im
Curious if there are fans made with less of a pitch to them.

 

[copper67sat]

Does the fan turn freely on the clutch or is it tight? On mine, the fan turns easily. It won't "spin", but it will easily turn about 1/2 a revolution if I flip a blade and I don't notice fan noise when it's running.

When the old clutch went bad, it locked up and the fan wouldn't turn separately from the clutch. Fan noise was very obvious in that case.

 

[RJRENTON]

Im
Curious if there are fans made with less of a pitch to them.

WHY would want LESS blade pitch as the fan's CFM (Cubic Feet per Minute) AND RPM determine how much air (and it's overall VELOCITY) determine the efficiency of the radiator's exchange ratio. Remember the basic fan law's:
Fan Law 1 tells us that the change in air flow rate of a fan is proportional to the change in speed of the propeller. If the propeller speed is increased by 10%, the air flow rate will also increase by 10%.

Fan Law 2 tells us that the change in total static pressure of the ventilation system will increase by the square of the change in propeller speed of the fan.If the propeller speed is increased by 10%, the total static pressure will increase 21%.

Fan Law 3 tells us that the change in horsepower required by the fan to turn the propeller will increase by the cube of the change in propeller speed of the fan. If the propeller speed is increased by 10%, the horsepower required to turn the propeller will increase 33.1%.

Slow down the fan and/or reduce the blade pitch and/or number of blades will result in hotter coolant temperature......just my opinion of course......or turn up the sound system volume......
BOB RENTON

 

[Ron H]

Checking some reviews I found on Summit and Amazon, only a couple reported about fan noise. One said after he ran it around for a while it quieted down some. Another mentioned adjustment. I gather these come in various ratings – heavier, lighter duty. You might check the reviews; many reported being happy with the setup. You could contact Hayden and see if they can be of any assist..

 

[dadsbee]

Fan law 4 is if it quits the pilot starts to sweat....