SAAC Forum

The Cars => 1968 Shelby GT350/500/500KR => Topic started by: shelbydoug on July 09, 2020, 09:43:38 AM

Title: C7ZX fan clutch
Post by: shelbydoug on July 09, 2020, 09:43:38 AM
I'm still using the original fan clutch. How can I test it to see if it needs a rebuild or not?
Title: Re: C7ZX fan clutch
Post by: Coralsnake on July 09, 2020, 10:03:22 AM
Are you have cooling issues?

Does the hub of the fan have more resistance on the shaft when you spin it?

Is it leaking oil?
Title: Re: C7ZX fan clutch
Post by: shelbydoug on July 09, 2020, 10:18:00 AM

Are you have cooling issues? I'm getting pissed off more then usual.

Does the hub of the fan have more resistance on the shaft when you spin it? It has resistance.

Is it leaking oil? No


Title: Re: C7ZX fan clutch
Post by: Shelby_r_b on July 09, 2020, 10:42:23 AM
Hey Doug. Great question. I watched someone test mine; though, I wouldn’t recommend his approach.

He let the car warm up and then, with his 4 fingers covered with a towel, he tried to get the fan to stop rotating while the engine was running. Yeah, not ideal. However, it did reveal that the clutch wasn’t engaging. I can attest to the fact that this procedure was not used to ops check the new clutch. 😉
Title: Re: C7ZX fan clutch
Post by: Coralsnake on July 09, 2020, 10:54:55 AM
Doug,

I dont think your fan clutch is the issue

But if you want to try the old “four fingers” test, you have another option 😀

I dont recommend a rebuild, the reproductions are very nice.
Title: Re: C7ZX fan clutch
Post by: KR Convertible on July 09, 2020, 11:05:17 AM
Don't make the same mistake that I did.  I bought a cheap Autozone fan clutch to diagnose the problem.  It actually ran a little hotter with the new one, so I assumed my clutch was good.  I spent a ton of time and money on a radiator re-core, rebuilding and recurving my distributor, putting larger jets in the carb, a 160 degree stat, new antifreeze with Water Wetter, and several bottles of Crown.

Still ran 230! I know people will argue that 230 is fine, but it shouldn't run 70 degrees over the stat temp. Since my car is a gold level car and I didn't want to add a different fan blade, I decided to buy one of Chris Brown's fan clutches.  Best money I ever spent! Dropped my temp to 195-200 degrees. 

The clutch had much more resistance than the Autozone POS.  Where's the head banging' emoji?
Title: Re: C7ZX fan clutch
Post by: 8T03S1425 on July 09, 2020, 12:05:19 PM
Doug,

I thought that my fan (C8OE-B) and clutch (C8ZX-A) assembly were fine. The clutch provided some resistance, but I didn't know how to measure it. The fan spun when the engine was running and it briefly (very briefly) continued to spin when the engine was shut down. It seemed fine to me, yet, according to the temp gauge in the dash, the engine would run hot.

As an experiment, I replaced the C8OE-B & C8ZX-A fan and clutch assembly with a fan (C9ZE-E) and clutch (C9ZE-B) assembly that I pulled out of a '69 Torino Cobra. My first finding was that the C9ZE-B clutch had slightly more rotational resistance than the C8ZX-A clutch. The C9ZE-E fan looked almost identical to the C8OE-B fan, as far as blade count, design, and pitch. My next and most important finding was that my engine ran cooler, as measured by the same temperature gauge.

Since I couldn't find someone who could objectively test my fan clutch, and I have a replacement that provides better cooling, I can take my time deciding if I want to buy another C8ZX-A clutch or have mine rebuilt.

Unless you find someone who can objectively test your C7ZX fan clutch against its manufacture specs, I'd recommend you try a similar test before you purchase a new clutch, have yours rebuilt, or move on to changing other cooling influencing components.

Steve
Title: Re: C7ZX fan clutch
Post by: shelbydoug on July 09, 2020, 12:47:42 PM
Thanks for all of your input. I need to ponder on this.

I'm not sure that I have a problem. The temp gauge is reading right in the middle with a 192 thermostat.

I'm not used to running those. Infra red is saying much lower 132 in the manifold. Carbs were peculating and I couldn't restart hot.

Since I have somewhat re-engineered the entire setup, I'm going through growing pains...again. I thought I was over this stuff?

I already insulated the carbs, changed out the ignition coil (wouldn't fire hot), and put in a 160 with water wetter.  It's much better but I'm still not comfortable with it so am looking for other conspiring gremlins like the fan clutch.

Still have hard hot restarting but engine is much cooler. About 1/3 reading on the gauge. Something else is going on here and am working on that.

I can't get it to idle under 950 hot. That shouldn't be.

There is resistence in the fan clutch with the engine off.

My son said to me, "too many parameters going on here".
Title: Re: C7ZX fan clutch
Post by: shelbyhertz66 on July 09, 2020, 01:13:10 PM
If you try the 4 finger test it won't be long until its the 3 finger test
Title: Re: C7ZX fan clutch
Post by: Coralsnake on July 09, 2020, 01:27:38 PM
Quote
Carbs were peculating and I couldn't restart hot.

That’s probably going to your corn based fuel on a hot day. Break that wallet open for a little racing fuel.
Title: Re: C7ZX fan clutch
Post by: gt350bp on July 09, 2020, 02:11:22 PM
Very happy with the Chris Brown reproduction fan clutch I bought for my KR with A/C.

Check out his website.

Don
gt350bp
Title: Re: C7ZX fan clutch
Post by: Coralsnake on July 09, 2020, 02:14:01 PM

http://www.brownsautobodyservices.com
Title: Re: C7ZX fan clutch
Post by: Shelby_r_b on July 09, 2020, 02:35:59 PM
If you try the 4 finger test it won't be long until its the 3 finger test

LOL!!
Title: Re: C7ZX fan clutch
Post by: cbrown on July 09, 2020, 03:17:36 PM

http://www.brownsautobodyservices.com

thanks Pete!!  Its an awesome site!!!   LOL