Fan Blade Disintegrated at 4,000RPM

71TexasBoss · Nov 25, 2024

Over the weekend I was doing some "spirited" driving in my Boss 351. On a strong launch from a red light as I was shifting to 2nd at 4,000RPM there was a loud pop under the hood I initially thought was a backfire. When I raised the hood later I saw a chunk of my D1ZE-8146-AA Boss fan shroud was missing. Closer inspection found one of the blades had split in half horizontally. The fan was an original and I assume a half-century old part couldn't take the stress.

So now I'm going to replace the stock fan with an aftermarket for safety and reliability. Any suggestions for an aftermarket HD cooling fan that is belt driven for a 351 Cleveland?

Thanks!

Stanglover · Nov 25, 2024

It looks like it might have been a flex fan. If it was, you're lucky a) you head wasn't under the hood and b) it didn't go right through the hood.
There have been people get killed by those fans. I've posted many times on how dangerous they are and information on a recall Ford did on flex fans. If it lasted 53 years, I'm surprised it didn't blow before. I used to work where they were made and I've personally seen the damage they can do WHEN they blow up on a test rig, like a blade buried into 4" of oak. Actually, I didn't know they put flex fans on 71 Mustangs, let alone a Boss. I can ask a friend who owns a Boss what is on his car.
If you're not that worried about being authentic, I might suggest a Hayden 2710 fan clutch and Derale 17118 18" fan

Sheriff41 · Nov 25, 2024

I have the Hayden-Derale setup @Stanglover mentions and it's been working great for me in our Texas summer heat.

71TexasBoss · Nov 25, 2024

Thanks for the fan recommendations. I'm more concerned at this point about safety and reliability instead of factory correctness. I'm lucky the errant blade didn't take out my hard-to-find Boss radiator.

Stanglover · Nov 25, 2024

71TexasBoss said:
Thanks for the fan recommendations. I'm more concerned at this point about safety and reliability instead of factory correctness. I'm lucky the errant blade didn't take out my hard-to-find Boss radiator.

Just out of curiosity, what is the difference between a Boss radiator and a standard 351C rad. Are there more cores, 3 instead of 2?

Now you also need to source a good shroud.

Sheriff41 · Nov 25, 2024

71TexasBoss said:
Thanks for the fan recommendations. I'm more concerned at this point about safety and reliability instead of factory correctness. I'm lucky the errant blade didn't take out my hard-to-find Boss radiator.

Yep, you're fortunate you didn't have any serious damage.

Cleveland Crush · Nov 25, 2024

Here's another vote for the above mentioned fan/clutch setup. Been running this same equipment for many years on mine.
PS-if interested this is what Ford issued in 1981 concerning the original early 1970's flex fans:

351c1971 · Nov 26, 2024

I also have the Hayden-Derale clutch/fan setup on my H code 351c. I recommend using all grade 8 fasteners for the installation..

Stanglover · Nov 26, 2024

351c1971 said:
I also have the Hayden-Derale clutch/fan setup on my H code 351c. I recommend using all grade 8 fasteners for the installation..

......... and pay attention to the placement of the bolt washers as mentioned in the instructions.
Also to make sure the blades are set to the correct depth within the shroud. I think it is 2/3rds.

Hemikiller · Nov 26, 2024

Another vote for the 2710/18" fan combo. I have an OE 69 Cougar fan on mine, but it functions the same.

I *might* have a D1ZE-AA shroud in my parts stash if yours isn't repairable.

mjlan · Nov 26, 2024

That sucks! I have no faith in any flex fan and will never use one.

I had a freind who had one fail on his freshly painted International pickup. Two blades came off, one went through the side of the hood the other straight through the top, tore through the metal like a can opener.

Be thankful that the shroud is the only thing that was lost, could have been a lot worse!

351c1971 · Nov 26, 2024

If I remember the Derale fan is rated for 8,000 RPM. That seems like a good safety margin.

roboconklin · Nov 26, 2024

71TexasBoss said:
Over the weekend I was doing some "spirited" driving in my Boss 351. On a strong launch from a red light as I was shifting to 2nd at 4,000RPM there was a loud pop under the hood I initially thought was a backfire. When I raised the hood later I saw a chunk of my D1ZE-8146-AA Boss fan shroud was missing. Closer inspection found one of the blades had split in half horizontally. The fan was an original and I assume a half-century old part couldn't take the stress.

So now I'm going to replace the stock fan with an aftermarket for safety and reliability. Any suggestions for an aftermarket HD cooling fan that is belt driven for a 351 Cleveland?

Thanks!

I’d check the engine mounts. Sounds like engine raised allowing the fan to connect the shroud

basstrix · Nov 27, 2024

My OEM flex fan let go back in about 1993. I was pretty lucky...all it did was put a couple of pinholes in the radiator core.

BUCKWHEAT · Nov 27, 2024

Would this Cleveland flex fan concern apply to my '73 302 also? I see the recall letter that would apply to my a/c 302 as well. Arrgh!

Stanglover · Nov 27, 2024

BUCKWHEAT said:
Would this Cleveland flex fan concern apply to my '73 302 also? I see the recall letter that would apply to my a/c 302 as well. Arrgh!

Best advice; if you have a flex fan, get rid of asap. Flex fans do not discriminate between engine displacement or even what make of vehicle. They are dangerous, period!

giantpune · Nov 27, 2024

The previous owner of my 69 mustang said hold his beer. Flex fan so big, he clearanced the shroud to make room for it.

Is this one of the explode-y ones? Or is this one fine?

Stanglover · Nov 27, 2024

giantpune said:
The previous owner of my 69 mustang said hold his beer. Flex fan so big, he clearanced the shroud to make room for it.

Is this one of the explode-y ones? Or is this one fine?

View attachment 95567

That's not really a "flex fan", but an aftermarket piece of junk.

basstrix · Nov 27, 2024

giantpune said:
The previous owner of my 69 mustang said hold his beer. Flex fan so big, he clearanced the shroud to make room for it.

Is this one of the explode-y ones? Or is this one fine?

View attachment 95567

There's an episode of Engine Masters where they tested some different fans. This looks a lot like the plastic/composite one they tested. This style had the 2nd largest loss of power (25hp) and a standard-duty fan clutch had the least (15hp). They tested something pretty close to our OEM flex fan it was right in the middle at about 20hp.

Fan Blade Disintegrated at 4,000RPM

Help Support 7173Mustangs.com:

Well-known member

Attachments

Well-known member

Attachments

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Attachments

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!