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Username Post: Is my 4 blade metal fan unsafe        (Topic#358784)
LSS1333 
Poster
Posts: 77

Reg: 05-13-15
11-11-19 03:59 PM - Post#2779999    

I have recently been driving my 63 impala SS convertible. The car originally came with a 283, but now has a fairly stout 383.

I reused my metal 4 blade mechanical fan and so far everything has been working fine. However, today I read that these metal (non clutch) fans are unsafe above about 4500 rpms. I also read that they only came on low performance vehicles.

Do I need a clutch fan since I will likely get over 4500 rpms on a fairly regular basis???



 


gchemist 
Senior Chevytalk Moderator
Posts: 24980
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-12-19 04:03 AM - Post#2780025    
    In response to LSS1333

Metal fatigue can be dangerous. A proper rotation plastic one with more fins can provide cooling. Or as I'm doing now, using a stock shroud go electric. Single or two speed.

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
japete92 
"5th Year" Silver Supporting Member
Posts: 1260
japete92
Loc: No. Virginia
Reg: 01-18-13
11-12-19 08:53 AM - Post#2780038    
    In response to LSS1333

  • LSS1333 Said:
I have recently been driving my 63 impala SS convertible. The car originally came with a 283, but now has a fairly stout 383.

I reused my metal 4 blade mechanical fan and so far everything has been working fine. However, today I read that these metal (non clutch) fans are unsafe above about 4500 rpms. I also read that they only came on low performance vehicles.

Do I need a clutch fan since I will likely get over 4500 rpms on a fairly regular basis???



You do not NEED a clutched fan, but you might like having one. The engine torque used to turn the fan when it is not needed for cooling (moving at speed) can be applied to propulsion. That's the advantage of the clutched fan. It's more accurately a 'de-clutched' fan.

Also, the 5 blade clutched fan adds a little better cooling at idle than the 4 blade because of the added blade.

I have a '383' in my '63 4 speed convertible. It ran great with my 'original' 4 blade fan. But, at idle in hot weather, the temps would raise higher than I liked. I replaced the 4 blade with a fix steel 6 blade fan. Idle cooling solved. I did not use clutched fan because it was more $ than the fixed, and at the time I had greater needs for the $.

I can (and do) run to red line (5400 rpm) w/o thinking about the fan. Change your fan if/when you choose.

I may install a OEM type 5 blade clutched fan in the future but it won't be because of any safety concerns. The 6 blade is a little noisy at higher rpms (when the clutched fan would 'cut off'). I don't hear it with the top down, but in the winter I notice it. So far it is not anything I want to spend $ on.

You did not mention exhaust but I also initially re-used my 2" ram horn manifolds and exhaust pipes to the muffler (tail pipes were 2" on all '63 V8s, including 409) on my 383. When I saved up the $, I replaced the manifolds and exhaust pipes with the 2 1/2". I kept the 2" tailpipes. I noticed the improvement in acceleration at rpms above about 3800. All those changes were simple and in-expensive because the car was designed to accept all of them.

Pete








 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17415
grumpyvette
Age: 71
Loc: FLORIDA USA
Reg: 03-16-01
11-12-19 09:11 AM - Post#2780039    
    In response to japete92

http://garage.grumpysperformance.com/index.php?thr...

visit a local u-pull-it salvage yard, a clutch fan off most chevy sb engines will bolt on, even some caddy, buick fans will work and most salvage yards will sell those clutch fans rather cheaply,
(ask the price before you go and pull the parts)

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
junky 
Valued Contributor
Posts: 3179

Loc: Northeast CT
Reg: 06-27-10
11-14-19 11:09 AM - Post#2780147    
    In response to LSS1333

I would caution you not to use a flex blade fan, because they can metal fatigue, and a blade can come off at any time. When I was an EMT, I had a call where a blade came off, and severely sliced a fellows arm as he was reaching over the fan to rev the engine. It wasn't a pretty sight, and I have no idea if he lost the arm or not. We delivered him to the hospital, where they took him directly into surgery.

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
TAT_2 
"18th Year" Silver Supporting Member, and Official CT Grim Reaper
Posts: 36148

Age: 66
Loc: "UNDER THE BOARDWALK"
Reg: 10-29-00
11-14-19 03:04 PM - Post#2780162    
    In response to junky

TRIED A FLEX FAN ABOUT 40+ YEARS BACK ON MY OLD 68 BB,BLADE CAME OFF & WENT THRU THE LOWER RADIATOR HOSE.GIVES ME THE CHILLS JUST THINKING ABOUT IT AS THE HOOD WAS OPEN & I WAS BLIPPING THE THROTTLE !!!



Attachment: 427_IN_68_VETTE.jpg (17.69 KB) 10 View(s)




09 PONTIAC- VIBE
08 PONTIAC- G6
93 VETTE - 40TH ANIV RUBY RED LT1/6SPD/RAG TOP
NEXT ?


*****
PREVIOUS VETTE'S 58,68,70,76,78,85,90
*****


Blessed are the cross-eyed, for they will see God twice


 
gchemist 
Senior Chevytalk Moderator
Posts: 24980
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-17-19 06:31 AM - Post#2780347    
    In response to TAT_2

While searching for a standard rotation plastic replacement, I found this website!
https://www.breeza.com/chevy-replacement-fan s/

They can custom build one for your application!

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
454cid 
Valued Contributor
Posts: 3129

Age: 46
Loc: West Michigan
Reg: 02-18-12
11-30-19 03:45 AM - Post#2781271    
    In response to LSS1333

I plan on swapping an 11-blade plastic fan into my truck. They're often white/natural-colored. I plan on using one of the newer spray paints that adheres to plastic to remedy that.

My steel and aluminum 9 blade fan has wobbled a bit for quite some time (maybe since new), and it's heavy, so swapping to something that is lighter and possibly move more air is my goal. I've also wondered about the aluminum blades letting go, although I suppose there's a chance on that happening with anything.

99 K3500 RCLB


 
IgnitionMan 
Valued Contributor
Posts: 3688

Reg: 04-15-05
11-30-19 09:04 AM - Post#2781282    
    In response to 454cid

If this engine has a fan clutch, the plastic fan might be too light for it to work correctly.



 
454cid 
Valued Contributor
Posts: 3129

Age: 46
Loc: West Michigan
Reg: 02-18-12
12-01-19 10:45 AM - Post#2781335    
    In response to IgnitionMan

  • IgnitionMan Said:
If this engine has a fan clutch, the plastic fan might be too light for it to work correctly.



I don't see it being a problem. It's a fan designed for use with a clutch.

99 K3500 RCLB


 
IgnitionMan 
Valued Contributor
Posts: 3688

Reg: 04-15-05
12-01-19 12:29 PM - Post#2781336    
    In response to 454cid

Other people do, as a different load weight would change the operating parameters for the clutch itself, just like the differences between a regular stock, and light weight flywheel affects engine operation.



 
1983G20Van 
Super Senior Member
Posts: 3794

Loc: Bedford, Texas, USA
Reg: 11-13-02
12-01-19 10:01 PM - Post#2781366    
    In response to 454cid

  • 454cid Said:
  • IgnitionMan Said:
If this engine has a fan clutch, the plastic fan might be too light for it to work correctly.



I don't see it being a problem. It's a fan designed for use with a clutch.



If anything the added blades will cause more drag and pull more cfm which causes the plastic fan to spend more time freewheeling. The higher drag will cause it to spin a little slower when it is freewheeling.

GM specified the same clutch with the 5 blade metal fan as they did with the 11 blade tow package fan on the GMT400 trucks. My Express van had the 5 bladed metal. I researched the clutch when I upgraded to the 11 blade plastic. 11 blade plastic cooled much better at slow speeds and hardly ever fully engaged. A/C was much colder after the upgrade around town.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


Edited by 1983G20Van on 12-01-19 10:02 PM. Reason for edit: No reason given.

 
gchemist 
Senior Chevytalk Moderator
Posts: 24980
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
12-02-19 04:49 AM - Post#2781368    
    In response to 1983G20Van

I'll add my own experiments with regards to fans. I've done two mechanical fan upgrades. One to a '96 4.3 Jimmy and a 2000 5.2 Ram. The Jimmy had the metal fan swapped for a 4.0 Explorer fan/clutch. The blades moved closer to the engine. The blades were half way into the shroud. Perfect location for cooling. Second, it was lighter too. Improvements were noticed in MPG and A/C cooling. It ran for years and never had cooling issues.
My current experiment, before upgrading to an Mark VIII fan, is a 5.2 Ram. GM used mechanical clutch cooling fans to '05. Most GM after '05 have electric fans unless they need heavy duty cooling. A used fan and new clutch bolted right onto the 5.2 water pump. As soon as the engine turned on I noticed the difference. Air going through the radiator is noticeable. The sound is like a large cooling tower sucking in air. The blades are half way into the shroud. The sound is different too. The large engine bay has an echo. Driving differences are noticeable too. The fan is engaged when turned on hot or cold. The fan releases in less than half the time/distance of the metal fan/clutch combo. The transmission shifts into higher gears at lower speeds too. The shifts are sooner and require less RPMs. The stock ECM made the changes. The biggest difference was OD/converter lock up. OD is engaged by a few MPH lower. The converter locks up at 5 MPH lower too. Acceleration from mid to WOT it noticeable too. The LS fan has less drag. After a month of fill ups, MPG gained is almost 1 in city driving. Not bad for a 5.2 pushing a 6000 lb extended cab truck. I'm going to run it until I have a chance to install a Mark VIII fan. It's mounted inside a stock shroud. It will have a dual temp Volvo relay set up for control. A/C fan cooling may use the lower speed setting or get a separate smaller condenser fan. The 5.2 is bound to get even better performance over the LS/clutch fan.

Attachment: fan1.jpg (128.57 KB) 4 View(s)


LS 9 blade fan vs 5 blade metal 5.2 Ram fan.


Attachment: fan2.jpg (107.38 KB) 2 View(s)


Test fitting an LS used fan/clutch combo on a 5.2 water pump.


'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
japete92 
"5th Year" Silver Supporting Member
Posts: 1260
japete92
Loc: No. Virginia
Reg: 01-18-13
12-02-19 07:31 AM - Post#2781380    
    In response to LSS1333

  • LSS1333 Said:
I have recently been driving my 63 impala SS convertible. The car originally came with a 283, but now has a fairly stout 383.

I reused my metal 4 blade mechanical fan and so far everything has been working fine. However, today I read that these metal (non clutch) fans are unsafe above about 4500 rpms. I also read that they only came on low performance vehicles.

Do I need a clutch fan since I will likely get over 4500 rpms on a fairly regular basis???



I've attached a screen shot from the '61 Shop Manual. It contains some info you may find helpful.

You do not require any exotic cooling on your engine as long as your timing is properly set.

Some general info:

The 'idiot light' come on at approx 240 degrees F

A 50/50 coolant mix at 15 psi does not boil until approx 260 degrees F.

My experience is coolant temps rise approx 10% from normal while idling in summer heat. For me 'normal' is 190 because I have alum heads and a 190 thermostat.

just trying to be helpful .

Pete




Attachment: fan_clutch_from___61_shop_manual.png (136.9 KB) 6 View(s)



 
65_Impala 
Very Senior Member
Posts: 4333

Reg: 12-29-02
12-02-19 09:58 AM - Post#2781388    
    In response to LSS1333

I would change to a clutch fan minimum simply for the performance gains. That stock 4-blade fan is easily using 30-40hp at higher rpm's, which is power that could be used to accelerate your car instead of turning the fan.

As for steel vs plastic. There is no problem changing between steel and plastic fans on the same clutch. By far, the main load the fan presents to the clutch will be the aerodynamic load (the resistance to moving air), not the weight of the fan. So, the aerodynamic loading will set the steady state speed the fan operates at. The weight will only affect the acceleration speed of the fan. With the thermal mass of the cooling system, it makes no difference in the cooling if the fan accelerates a little faster of slower.





 
IgnitionMan 
Valued Contributor
Posts: 3688

Reg: 04-15-05
12-03-19 10:09 AM - Post#2781436    
    In response to 65_Impala

Opinions, and real fact vary.

Before the poster directly above his goes on his pulpit and calls me a liar, yet again, please realize my facts come not from myself, but from all 4 American car makers, and a few Japanese companies that have tested fans, A/C fan clutches, and a lot more about them, including the differences between fan drive ratios, fans made of stamped steel, cast plastic, and other factors.

We had ongoing tests on this subject when I worked at GM for 5 years.

Now, before we get the "Post those results", why don't all of us simply investigate on our own, and come to our own decisions about how it was, and is done, and actually works.



 
65_Impala 
Very Senior Member
Posts: 4333

Reg: 12-29-02
12-03-19 07:10 PM - Post#2781468    
    In response to IgnitionMan

If you search the internet, you can find test data proving fixed fans can cause a 30-40hp loss and there are multiple other posts that already illustrate how changing from a steel to a plastic fan on a clutch is an improvement, not a failure, because aerodynamic drag IS the main load on the clutch. Just like changing a flywheel affects the acceleration rate of the engine, changing the fan weight on the clutch will only affect the acceleration rate of the fan.

Either way, good job with yet another useless insulting post!



 
55Redneck 
Ultra Senior Member
Posts: 14559

Age: 59
Loc: Hedley B.C. Canada eh!
Reg: 06-24-00
12-04-19 06:47 AM - Post#2781478    
    In response to 65_Impala

You two need to go into a dark room with baseball bats and see who comes out.

In memory of Mike McVeigh, the Mad Springwhacker.


 
55 Shaker 
Member
Posts: 1512

Age: 70
Loc: north central IL.
Reg: 03-13-06
12-04-19 07:10 AM - Post#2781480    
    In response to 55Redneck

  • 55Redneck Said:
You two need to go into a dark room with baseball bats and see who comes out.


Or kiss and make up.


The older I get, the more dangerous, I am !!!!


 
rcr3 
"15th Year" Silver Supporting Member
Posts: 3208
rcr3
Age: 68
Loc: MANHEIM PA. U.S.A.
Reg: 11-24-02
12-04-19 10:53 AM - Post#2781487    
    In response to 55 Shaker

Or put each other in the lead box and MOVE ON!

'67 Camaro survivor
'06 Z71 Sierra Ex Cab
'37 Chevy cp.SOLD!!6/7/14
'74 Nova Custom cp.
'73 Nova pro-street project
'17 Chevy Trax LT
'00 S10 Ex cab






 
Chevelle 
ChevyTalk Community Manager
Posts: 971
Chevelle
Loc: San Clemente, CA
Reg: 08-31-13
12-04-19 07:57 PM - Post#2781515    
    In response to rcr3

Closed as a result of two members not being able to get along. Sounds childish doesn't it.

p.s. if the insulting continues the next one who starts it will get the boot.

Chevelle
Community Manager

I'll be happy to help just ask.

Click here to become a Gold Supporting Member and we'll turn off the ads at the top!!!


 


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