[amatojm]

Does anyone know if a clutch fan was an option in '74? I purchased my car with a 4 blade mechanical. Not sure if this is correct either. Mine has the L65 engine if that makes a difference.

 

[RifRaf]

My 74 nova with a 350 sbc originally was equipped with a 19.5" - 7 blade clutch fan and a 21" diameter fan shroud.
The original fan with a replacement Hayden clutch shown in the image below.

A replication of the fan I am using can be obtained from Classic Industries (Part #3991431).

1971-1979 All Makes All Models Parts | 3991431 | 1971-79 OER Authorized 19-1/2, 7 Blade Fan | Classic Industries

OER® Authorized reproduction fan blade which was installed as original equipment on various GM models with 19-1/2 diameter, 7 blade fan. Chevrolet Passenger Car Applications: 1971 Passenger with 36 Amp Except Police/Taxi 1971-74 Passenger V8 with C.A.C. 1971-74 Taxi/Police V8 Except C.A.C. 1975...

www.classicindustries.com

 

[amatojm]

Thanks! That's exactly the route I am going. Just wasn't sure if it was "correct". Seems there's no real rhyme or reason for type of blade and whether it's mech or clutch.

Do you think there is a real difference between that 7 blade and the 6 blade derale fan?

My 74 nova with a 350 sbc originally was equipped with a 19.5" - 7 blade clutch fan and a 21" diameter fan shroud.
The original fan with a replacement Hayden clutch shown in the image below.
View attachment 404921
A replication of the fan I am using can be obtained from Classic Industries (Part #3991431).

1971-1979 All Makes All Models Parts | 3991431 | 1971-79 OER Authorized 19-1/2, 7 Blade Fan | Classic Industries

OER® Authorized reproduction fan blade which was installed as original equipment on various GM models with 19-1/2 diameter, 7 blade fan. Chevrolet Passenger Car Applications: 1971 Passenger with 36 Amp Except Police/Taxi 1971-74 Passenger V8 with C.A.C. 1971-74 Taxi/Police V8 Except C.A.C. 1975...

www.classicindustries.com

 

[RifRaf]

Thanks! That's exactly the route I am going. Just wasn't sure if it was "correct". Seems there's no real rhyme or reason for type of blade and whether it's mech or clutch.

I think the variation in fans had to do with the vehicle's original set-up from the factory... HD cooling, AC, etc.
I will verify that my fan and shroud combo had no problem keep my 500 HP 400 sbc at 180° at long idle periods during the hottest summer days.

Do you think there is a real difference between that 7 blade and the 6 blade derale fan?

I'm not familiar with the 6 blade derale fan... can you post a link to one.

 

[amatojm]

I think the variation in fans had to do with the vehicle's original set-up from the factory... HD cooling, AC, etc.
I will verify that my fan and shroud combo had no problem keep my 500 HP 400 sbc at 180° at long idle periods during the hottest summer days.

Well that says something, for sure!

I'm not familiar with the 6 blade derale fan... can you post a link to one.

19 Standard Rotation Fan Clutch Fan, Black

19 Standard Rotation Fan Clutch Fan, Black Standard Rotation 19" Fan Clutch Fan 17119

derale.com

It seems to be more of a universal fan
Specs show this one as 19 1/8 diameter with a 27* blade pitch and a total blade height of 2 inches.

Cost on amazon is roughly $40 less than the 7 blade.

 

[RifRaf]

I agree that the Derale Fan seems to be a universal fit.
Hard to say how the Derale fan would work compared to the 7 blade fan... maybe someone who has used the Derale fan will chime in.
Suggest doing a Goggle search on "Derale 17119 and read the reviews. Most reviewers seem to like this fan, but some complain that installing the clutch was tight... sometimes requiring filing that could throw off the balance of the fan.

What ever fan you decide to purchase, I do recommend the Hayden 2747 Clutch Fan. I am currently using this model. It's the heavy duty version... but it does not make any more fan noise that the standard version clutch fan (Hayden 2705). I have used both clutch fans.

Amazon.com: Hayden Automotive 2747 Premium Fan Clutch: Automotive

Buy Hayden Automotive 2747 Premium Fan Clutch: Clutches - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[amatojm]

I agree that the Derale Fan seems to be a universal fit.
Hard to say how the Derale fan would work compared to the 7 blade fan... maybe someone who has used the Derale fan will chime in.
Suggest doing a Goggle search on "Derale 17119 and read the reviews. Most reviewers seem to like this fan, but some complain that installing the clutch was tight... sometimes requiring filing that could throw off the balance of the fan.

What ever fan you decide to purchase, I do recommend the Hayden 2747 Clutch Fan. I am currently using this model. It's the heavy duty version... but it does not make any more fan noise that the standard version clutch fan (Hayden 2705). I have used both clutch fans.

Amazon.com: Hayden Automotive 2747 Premium Fan Clutch: Automotive

Buy Hayden Automotive 2747 Premium Fan Clutch: Clutches - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I'll take your suggestion on the 2747 clutch!

I agree that any filing on the fan would cause and imbalance.

I see the OEM fans on ebay. Some people are charging gold for them. Maybe due to a certain date code?

I think I will order up one of these Derales. I have a Derale 17" fixed blade(not clutch) that I used on my stand and it seemed to move quite a bit of air. Way more than the ebay special electric that came with my old champion radiator.

I wish fan blades could be spec'd by CFM. But RPM and pulley size plays to much into that.

Oh well, good to know the clutch was an option for my year!

You're always a wealth of information, Rifraf!

 

[RifRaf]

Sounds good!
Please keep us posted on how the Derale 17119 works out for you (fit, overall air flow, etc).
I'm sure it would provide useful information for those looking at options for economical clutch fans.

 

[amatojm]

Sounds good!
Please keep us posted on how the Derale 17119 works out for you (fit, overall air flow, etc).
I'm sure it would provide useful information for those looking at options for economical clutch fans.

Got the new fan yesterday. It looks really good. Great angle on the blades and should pull plenty of air and it feels very solid and sturdy.

Here is where things go south. The fan is made with these tangs. Seem like they might be used to locate the fan on some clutches, but they make it impossible to install on a stock sbc clutch. A little work with a sanding bit on a dremel and a dab of primer to prevent rust takes care of it but it certainly seems like something that doesn't really need to be there.

To any reviews that state concern on removing these throwing off the balance of the fan, I really think that's a non-issue. Sand them all down evenly and it shouldn't be a problem at all.

 

[RifRaf]

Thanks for providing a detailed update on the installation of this fan!

 

[amatojm]

Thanks for providing a detailed update on the installation of this fan!

Well ill be dipped if I didn't strike a little gold while having some salvage yard therapy today during lunch. Just sitting in the bed of a '79 half ton pickup.
The yard let me go for two crinkled up $10 bills.