Some fan clutch air flow rate measurements

Here are some airflow rate numbers for two different fan clutches.

Testing conditions:

• Kestrel 1000 anemometer.
• Front grill removed.
• Hood closed.
• Anemometer placed against A/C condenser at the same location for each measurement. Location roughly corresponds to mid-height of the radiator and about mid-distance between the base and tip of the fan blade extent. I can post a photo if anyone wants to see the location.
• Engine up to full temperature for at least 15 minutes prior to all measurements.
• About 70F ambient air temperature.

Results:

NAPA 272318 XJ 4.0L fan clutch. This is not the ZJ fan clutch. The 272318 is the same as the Murray 2625 fan clutch available at O'Reilly and Advance Auto. I've been using this fan clutch for about a year now.

• Idle (about 670 rpm): 560 ft/min.
• 2000 rpm: 1150 ft/min.

US Motor Works (USMW) 22148. This is the same as the Autozone Duralast 922625 and the Crown 52003205. It takes up no more space than the NAPA 272318.

• Idle (about 670 rpm): 520 ft/min.
• 1500 rpm: 1300 ft/min.
• 2000 rpm: 1750 ft/min.

I wish I had performed more airflow measurements of the NAPA fan clutch to make a better comparison at lower rpms where fan speed is going to be more important. But that aside, the USMW clutch still clearly much pulls more air at lower rpms. Probably from 1000 rpm upward, the USMW 22148 significantly outflows the NAPA 272318.

I have not tested the NAPA ZJ fan clutch because it won't fit with my Cold Case radiator. However, if I were to guess, I'd say that the USMW creates as much air flow as the ZJ fan clutch at 1000+ rpm. At idle, the ZJ fan clutch likely flows more.

Fan clutch photos.

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Retired out of a Napa and cause of that have a tendency to buy most of my parts there.
I want to say that is the same fan clutch I used in my '00 and that, at least back then, was a rebranded Hayden.

Another retired Napa employee here I was thinking we had Murray reboxed as temp but I could be mistaken I retired In 2019 after 35 years with genuine parts company.

jeep ride said:

Another retired Napa employee here I was thinking we had Murray reboxed as temp but I could be mistaken I retired In 2019 after 35 years with genuine parts company.

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About 2018 for me after about 12 years at a privately owned one.
I could be totally wrong about that though.
I thought I saw something somewhere that made me think that though.
Plus you know more then most how Napa will change suppliers.
For instance I am almost positive that Napa radiators were rebranded Spectra's.
But awhile back I noticed the part number for my '00 had changed and think that they no longer are.

I was just going to ask you if you worked at a jobber store I worked for GPC when I first started with them we sold modine radiator 's I have no idea what brand they sell now everything we sold was reboxed from someone else.

jeep ride said:

I was just going to ask you if you worked at a jobber store I worked for GPC when I first started with them we sold modine radiator 's I have no idea what brand they sell now everything we sold was reboxed from someone else.

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I worked for TRW/Federal-Mogul for 13 years. My customer was Big A Auto Parts, nationwide.

I spent the majority of my time doing changeovers. Re-boxing doesn't seem right to people outside of our industry but we know it is an accepted practice.

During my time, I re-boxed Moog to TRW that had been TRW that the Moog guys re-boxed previously. :looney:

Sounds like Napa the way they operated their stores they had people like you doing the same thing I'm thinking there was a Big A store in Charleston WV at one time but I'm not sure.

Here's a pic of my factory XJ compared to a HD ZJ. I run a Griffin radiator and had no problem with fitment between the pump housing and the radiator.

RCP Phx said:

Here's a pic of my factory XJ compared to a HD ZJ. I run a Griffin radiator and had no problem with fitment between the pump housing and the radiator.

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Wow! That is huge! Is it loud?

Old Man Minimalist said:

I worked for TRW/Federal-Mogul for 13 years. My customer was Big A Auto Parts, nationwide.

I spent the majority of my time doing changeovers. Re-boxing doesn't seem right to people outside of our industry but we know it is an accepted practice.

During my time, I re-boxed Moog to TRW that had been TRW that the Moog guys re-boxed previously. :looney:

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Yeah, no telling who is making the NAPA/Murray clutch, but for sure USMW is making their clutch. Both the USMW clutch and the Duralast both have "USMW" etched onto the clutch. And I spoke with USMW about their clutch, and they said that they are the manufacturer.

RCP Phx said:

Here's a pic of my factory XJ compared to a HD ZJ. I run a Griffin radiator and had no problem with fitment between the pump housing and the radiator.

Click to expand...

The ZJ fan clutch would be an overly tight fit with the Cold Case radiator. There's 0.5" clearance from the front of the XJ fan clutch (either the NAPA or the USMW) to the back of the Cold Case radiator on my XJ, and the ZJ fan clutch sticks out another 0.33" further than the those XJ fan clutches (I measured all three clutches). Using a ZJ fan clutch with the Cold Case radiator would leave a gap of ~0.2" at the very best. cal modified his Cold Case radiator to sit further forward to leave more room for a ZJ fan clutch. He's got several post showing the mods to the radiator.

Old Man Minimalist said:

Wow! That is huge! Is it loud?

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Not at all!