5 blade to a 7 blade well it help

[33 IMP]

I think I would add a shroud before I did a fan change.
If you already have both fans, give it a try....and report back.

 

[Tony Tee]

Google said , a 7 blade fan will move more air than a 5 blade fan of the same pitch and diameter and rpm. But the 7 blade fan has more drag. Meaning more energy required to turn it.
And crop duster and cargo aircraft have more blades on their engines.

 

[WileE]

Oh yeah, car radiators and planes are the same thing. How silly of me to think of automotive applications on a car forum.

It's about air movement. Also, drag and turbulence. Properties of air movement learned in aerodynamics.

And crop duster and cargo aircraft have more blades on their engines.

Most crop duster and cargo planes have 4 blade props.

 

[Kern Dog]

Good thing that radiator fans don’t double as propelling devices.
I looked… the fan in my 2007 Dodge truck is a 5 blade. I have seen Cummins and 5.2-5.9 trucks with huge fans with more than 8 blades. There must be some science behind that to warrant the design.

 

[68 Sport Satellite]

We're not likely to solve this debate here with unanimous agreement, however, here's another view from the A-bodies forum and I see some merit in it:
5 blade vs 7 blade clutch fan
Post #17 by RustyRatRod: Actually, rumblefish is right. The 5 blade offset fan was made for two purposes. First, it moves more air than the symmetrical 7 blade fan. That's why it was sold as part of the performance package in the Direct Connection and MP catalogs. And yes, a side benefit to the offset blades is that they made less noise. But not by much.

I also believe fan diameter matters a lot. Some of the Mopar fans I've seen are 17" and some are 18". The 18" improvement in cooling is noticeable.
I will also reiterate that blade pitch is EXTREMELY important. Not only can it affect air flow and engine cooling, it also has a big effect on fan noise.
@Kern Dog knows this as he installed the Vintage Air A/C in my car, along with the required A/C pulley swaps, as well as swapping in a clutch fan for my previous fixed fan. The first fan he installed in my car along with the required smaller diameter A/C pulley sounded like a jet aircraft taking off when revving the throttle. It was unbearable. Luckily, KD had a spare 7 blade clutch fan with a less aggressive blade pitch angle. Once he swapped that in, everything quieted back down, but engine cooling remained excellent.

 

[twecomm]

Perhaps what's needed here is a "Renton-esque explanation". I believe that this is his area of expertise. If you research the facts, a 5 blade moves more air vs: a 7 blade fan.

 

[pedal2themetal]

HI,
I've decided to work on getting a shroud for it.. There's is one on E bay but the shipping charges are over $100.. I'm going to check the U pull it yards here..

 

[Some Car Guy]

When is it overheating? In traffic or going down the road?

 

[RJRENTON]

Google said , a 7 blade fan will move more air than a 5 blade fan of the same pitch and diameter and rpm. But the 7 blade fan has more drag. Meaning more energy required to turn it.
And crop duster and cargo aircraft have more blades on their engines.

A 7 blade fan REQUIRES more horsepower to move the additional amount of air. The correct term is not drag but hp required....fyi. crop dusted planes to generate more lift at a slower air speed and weight.
BOB RENTON

 

[pedal2themetal]

When is it overheating? In traffic or going down the road?

HI,
Just did some high traffic with lots of stops and it's boiling in the radiator. gauge went up to like 3/4 of the way.. 185* stat.
Maybe I should bite the bullet and get a bigger radiator .. tho I didn't ever have that problem before the cam change? Once it cools down I'm going to check the timing might be to much tho it starts right up and doesn't ping.. Well it is harder to start when warmed up so maybe timing is to high..

 

[dodgeboy440]

Google said , a 7 blade fan will move more air than a 5 blade fan of the same pitch and diameter and rpm. But the 7 blade fan has more drag. Meaning more energy required to turn it.
And crop duster and cargo aircraft have more blades on their engines.

If Google says so ,,,,,,, it’s gotta be true!

 

[Kern Dog]

The 5 blade versus 7 does have me curious. I have used both and did not have overheating with either.
Basic bonehead sense leads me to think that more blades means it will pull more air through the radiator. Once the vehicle is moving, I don’t see the greater fin count being a problem.
This assumes the same angle of the blades.
The job of the fan is to pull ambient air through the radiator. I’m skeptical that fewer blades would pull as much air. Ma Mopar fitted the higher HP cars with the 7 blade fan. Cars with the Towing package got that too.

 

[RJRENTON]

If Google says so ,,,,,,, it’s gotta be true!

Not necessarily true........google says: biodegradable agricultural slag is loaded with beneficial nutrients......if......you can get use to the aroma and taste.......?????......like beauty.....it's up to the individual.........or do you believe in everything you read....????....
BOB RENTON

 

[Kern Dog]

Sarcasm detector FAILED.

 

[33 IMP]

HI,
Just did some high traffic with lots of stops and it's boiling in the radiator. gauge went up to like 3/4 of the way.. 185* stat.
Maybe I should bite the bullet and get a bigger radiator .. tho I didn't ever have that problem before the cam change? Once it cools down I'm going to check the timing might be to much tho it starts right up and doesn't ping.. Well it is harder to start when warmed up so maybe timing is to high..

General rule of thumb:
If it overheats at idle/in traffic, you need more fan/shroud.
If it overheats on the highway, you need more radiator.
In my cars, I run the biggest, widest radiator that will fit between the frame rails.

 

[Kern Dog]

That is an interesting perspective.

 

[Some Car Guy]

HI,
Just did some high traffic with lots of stops and it's boiling in the radiator. gauge went up to like 3/4 of the way.. 185* stat.
Maybe I should bite the bullet and get a bigger radiator .. tho I didn't ever have that problem before the cam change? Once it cools down I'm going to check the timing might be to much tho it starts right up and doesn't ping.. Well it is harder to start when warmed up so maybe timing is to high..

Have you looked at the plugs and done any jetting with the new cam?

It will be harder to start if it’s running hot, even if not boiling over.

I’d go over the tune, timing and jets.

 

[Curiousyellow71]

A simple way to look at this is fan speed is directly related to flow. Adding blades is similiar to turning the fan faster. Yes..a 5 blade of a more efficient design can move more air then a poorly designed 7. Design factors that change cfm are: blades #s, air foil fan blade shape, pitch and width of the blades, diameter and Hp. If your belt can only pull a certain amount of hp..its only going to move the same amount of air and slip when your beyond the hp capacity. Typically a fan with more blades has smoother flow and can overcome more pressure. I designed a fan that I could add/ remove blades for a axial style fan..more blades moved more air.

 

[pedal2themetal]

HI,
I just had a nightmare over night..
I did have the heads done as well as changing the cam.. Could I have installed the head gaskets upside down??????
Some car guy... I'll put a timing light on it today. I didn't do any jetting change. carb is a 450 QF.

 

[Curiousyellow71]

HI,
I just had a nightmare over night..
I did have the heads done as well as changing the cam.. Could I have installed the head gaskets upside down??????
Some car guy... I'll put a timing light on it today. I didn't do any jetting change. carb is a 450 QF.

As far as I know bb mopar gaskets are reversible. So you can't really install them upside-down. Some engines have a front and back way to install them like a Ford FE.
Timing certainly could affect the engine temp. Is this a quick fuel 450cfm on a big block???
Thermostat quality isn't the best these days either. It could be going bad and just a coincidence that the issues showed up at the same time. Probably unlikely so..but we often over think issues. At least I do all the time.Lol