Duramax Fan for stock shroud

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L31MaxExpress

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So I did a thing and trimmed the Duramax fan to fit in the 01-02 Express fan shroud I am running. It is now the same diameter as a GMT400 tow package fan. I measured several times used a T-gauge like you use to set floats on a carb to get a consistent distance for a clean radius, then cut the blades with a pair of sharp scissors. I then used the clipped blade as a templete to scribe the others so they were as close to identical as I could get. Duramax fan is going back on. Compared to the 11 blade GMT400 fan or even my current 06 F150 fan I am sure the Duramax fan will move alot more air as it still has way more surface are to the blades and more aggressively pitched blades as well.

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Supercharged111

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Sure would be nice if I had that much room in the dually for a good electric puller. The dmax fan is just bolt in and go for trucks, right? I want to do this and put some hood louvers on the dually. Last I had it out towing in the wind in 100 degree heat the water was a good 210 which took oil and trans up with it. Fan was cycling on and off and it's no good at a standstill.
 

L31MaxExpress

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Sure would be nice if I had that much room in the dually for a good electric puller. The dmax fan is just bolt in and go for trucks, right? I want to do this and put some hood louvers on the dually. Last I had it out towing in the wind in 100 degree heat the water was a good 210 which took oil and trans up with it. Fan was cycling on and off and it's no good at a standstill.
The Duramax fan is 21". I have a 3500HD fan shroud on my Tahoe that fits the 34x19 radiator and it clears. Measure first. The clutch I used was for a TBSS as the bolt circle is larger. Not sure the circle on a standard big block one. My Tahoe has always had the factory pusher fan. It is a 2wd LT but was ordered from GM with the heavy duty cooling package and tow package. I think the police Tahoes had the same cooling setup.
 

Supercharged111

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The Duramax fan is 21". I have a 3500HD fan shroud on my Tahoe that fits the 34x19 radiator and it clears. Measure first. The clutch I used was for a TBSS as the bolt circle is larger. Not sure the circle on a standard big block one. My Tahoe has always had the factory pusher fan. It is a 2wd LT but was ordered from GM with the heavy duty cooling package and tow package. I think the police Tahoes had the same cooling setup.

My shroud is almost 22" ID, so no problem there. The problem is the clutch that my truck has, which is not the spin on type that I assume you have which would mean that the TBSS clutch is a no go.

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df2x4

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Honest question, not trying to criticize... I know you used a template and made the alterations to the blades as identical as possible, but isn't there a chance this could throw the fan out of balance? IIRC I've seen a video where someone had issues as a result of clutch fan modification like this but I can't remember where... Maybe PFI Speed?
 

GMCTRUCKS

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Get ready for your water pump to give out the fan isn’t balanced correct now.

Wetter Water look it up.

Clean out the Radiator clean bugs off condenser and Radiator
 

454cid

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Balance is important, but I'm thinking that as long as he's careful (and it sounds like he was) that a slight imbalance won't make a difference here.

Here's why I think that:
The fan is light weight, so the mass difference between blades won't be much.
I'm not convinced the factory fans are balanced all that well to begin with.
My fans don't even rotate in a single plane, and I don't seem to have issues with things coming apart.
He's not racing, this is a road vehicle so RPM's will not be all that high. If he were hitting 5K/6K then I'd be much more concerned.
It's not my vehicle, so if it blows up it's not my problem :cool:
 

Supercharged111

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Balance is important, but I'm thinking that as long as he's careful (and it sounds like he was) that a slight imbalance won't make a difference here.

Here's why I think that:
The fan is light weight, so the mass difference between blades won't be much.
I'm not convinced the factory fans are balanced all that well to begin with.
My fans don't even rotate in a single plane, and I don't seem to have issues with things coming apart.
He's not racing, this is a road vehicle so RPM's will not be all that high. If he were hitting 5K/6K then I'd be much more concerned.
It's not my vehicle, so if it blows up it's not my problem :cool:

Plus his methodology took that into account. He used scissors, not a wheel to cut it, so that eliminates the variable of how much material disappeared. He's definitely aware of the risk he took.
 

L31MaxExpress

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Get ready for your water pump to give out the fan isn’t balanced correct now.

Wetter Water look it up.

Clean out the Radiator clean bugs off condenser and Radiator
Condenser and Radiator are new. Hottest the engine got was 191°F with the electric fan off and 185°F with it on.

Trimmed fan is runing smoothly.

I am aware of the risks of an unbalanced blade but it did not look like GM made any attempt to balance it at all. The fan still has chunks of molding flash like a model kit.

I was putting the dash back together after replacing the cluster bulbs with LEDs, had it sitting in the shop, doors open and fired it up. I let it cool down with the puller fan on. Commanded the fan on with HP Tuners. Let it run for about 10 minutes. Inside of the van was very ice boxish. Then I commanded the fan off and waited. After about 10 minutes. The air had warmed up a bit and pressures had creeped up but were still holding around 275 and 42.

Also worth mentioning with 33% underdrive on the water pump pulley, I can spin this 6,000 rpm and the fan is still only turning as fast as a stock one at 4,000 rpm. The power loss is less because of the underdrive. The big diesel fan is pitched more steeply because of the slower engine speeds of the Duramax. Even if the clutch was fully engaged at 2,100 rpm cruising down the road the fan is only spinning ~1,400 rpm. If I rev this 383 with close to 500 ft/lbs of torque over 3,500 rpm I am in one hell of a hurry to get somewhere.

Inside the shop, weather in the area at the time I tested it.

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Left most vent, center vent is several degrees colder at this point.
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After switching off the 16" fan. Center vent which had been sub 40 about 10 minutes earlier. Honestly that is more than 10°F colder than the stock van with R134a would have ever cooled sitting stationary at idle in this temperature. After 10 minutes, I commanded the idle to 1,500 rpm. The IAC opened to 310 steps but the engine would only turn 1,350 rpm. I let it run for about 5 minutes at 1,350 with the fan commanded on again. The center vent dropped to ~36°F and the compressor cycled. After 5 minutes at 1,350 rpm, high side pressure was about 240-250 and the low side was below 30 psi and the duramax fan was screaming like a medium duty truck.

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