“Duramax fan”

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L31MaxExpress

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There is another fan in GMs parts bin that moves a ton of air. GM put them first on the TBI 454s, then on the CPI Astro vans and later on the 8.1s. Its a nice upgrade from the little 5 bladed fly swatter as well. It is the size and pitch of the 5 blades that make it pull more air. It fits the standard 3.25" bolt circle of a standard reverse rotation fan clutch.

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Schurkey

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Don't forget, when selecting a fan clutch, that the water pump pilot hole size/depth is every bit as important as the water pump, and fan bolt-circles, in terms of fitment.

Some fan clutches come with a bushing that can be dropped-into the pilot hole, making them compatible with a smaller-sized pilot on the water pump.
 

PlayingWithTBI

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Fan clutch for a 454, probably.
Now you guys got me thinking :rolleyes:

I went to Rockauto.com, looked up a severe duty clutch for a 1988 C1500 5.7L and one for a C3500 7.4L - they list the same reverse rotation clutches for both, ha ha. So, I looked at the HD vs Severe Duty. Look at the percentages which they turn the fan when engaged and disengaged.

HD
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Severe Duty
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So, according to their pictures, I may have a Severe Duty clutch, yay!:waytogo:
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Orpedcrow

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Yes, the 11 blade fan from the 98 C1500 bolts right up to the TBI clutch in my 88. I don't remember what clutch it has (I think it's HD) but has been working fine for months now. At least it got me through the desert summer with no issues. I don't know about fluid dynamics involved in spinning the fan but, I wouldn't think you can hurt it with the little bit of added resistance from the 11 blade fan, we'll see.
Thank you, so I guess I’ll just order a fan (11 blade) and heavy/severe duty clutch for my 97 lol
 

Orpedcrow

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154672 fan clutch (GM genuine)
1580739 fan blade (GM genuine)

Both parts were listed under my vehicle description on Rockauto.
Did you ever get this set? If so, how's it been working?
Oh man it’s great. Really quiet, moves plenty of air. I can sit idling in the Texas sun with the a/c on full and the temperature doesn’t even quiver.

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