Does the Duramax fan need a spacer?

[GMC Hauler]

I recently put a new fan clutch and the duramax fan on my sub. I noticed that the fan blades stick out from the shroud about an inch. I don't remember the stock fan doing this. Has anyone noticed this? Should I get a spacer for the fan clutch?

[JoeyD]

It's normal. Stock fan sat in the same place.

[diesel65]

Joey,
GMC Hauler is correct in observing that the fan blade is sticking out more than the stock blade.
I did the D-max blade conversion myself and found that the fan blade was now kissing the resonator tube that comes off of the air intake, I ended up putting a couple of washers under the tab of the tube to raise it up.

GMC Hauler, I left mine sticking out and it is working very well, I think as long as there is a shroud around the fan blade to prevent air spillage, it is not critical how deep the blade is in the shroud.
Just make sure it is not rubbing against any thing as I mentioned above.

I am very happy with new blade because it is alot quieter than the stock steel blade was.

[Cowracer]

The cooling fan on engines function more like an axial flow or 'centrifugal' air pump than a linear flow fan.

Most of the air moved by the fan is displaced axially around the circumference of the fan disc. Comparativly little is "blown" back at the engine.

The blades must be clear of the shroud or else you will severly restrict air flow from the fan (and thus through the radiator).

I have seen many instances in dirt-track racing where someone made a shroud out of sheet metal that extended some inches rearward of the fan, and had monumental cooling problems. IMHO the optimum fan shroud will extend to about the halfway point on the blades.

Having the shroud one inch too short is no big deal, but having the shroud one inch too long will kill your flow.

Tim

[JoeyD]

I did not notice any difference in the position when I did mine and it didn't hit the silencer tube.