[leeklm]

I am curious to hear any recommendations from those who race their cars with mechanical cooling fans. I currently run a stock 7-blade fan with thermal clutch (heavy duty I believe), which works very well. However, I have been getting a few strange "vibes" once in a while around 5-6K just before shifting. The fan & newer Hayden Clutch seem to be in good shape, but my troubleshooting is pointing to a possible scenario with the clutch engaging more than it should at high RPM.

Because the current system has worked so well, I am hesitant to go electric, and then introducing other issues like potential need for larger alternator, fitting an electric fan while trying to keep a "stock" look, etc. My car spends as much time on the street as it does at the track, so looking for the best of both worlds.

For those running mechanical fans at the track, will a non-thermal clutch run fewer rpms as the engine RPM approaches 5K compared to thermal? Also, if running a thermal type clutch, I am assuming the "standard" duty clutch would be preferred as it turns the fan at a slower rate compared to the heavy duty or severe duty clutches?

I have a large radiator and full shroud, so the car has been pretty easy to cool. I am not too concerned with cooling ability, but of course that could change quickly if removing the current clutch fan

Thank you!

[Don 79 TA]

one option might be to look at a clutch setup for a diesel
a few of my friends were using these for FAST class racing
supposed to kick off after 3500 rpms
i use e-fans, but as you said you will more than likely need/want an alt. upgrade

[JSPONT]

I just switched from electric to mechanical. There are pros and cons to both. My car is 99% street, I have a big amp alternator. My electric fan went bad (while I was in traffic). I bought the 7 blade with a hd clutch from a member here. The car runs at 175-180, the shroud I made fits "loose". It ran 5 degrees hotter with the electric because the shroud covered the radiator fully.
If it is a track car only, you need good battery, and you can cool easy between runs, but it strains the battery which the ignition system needs.
With the mechanical after you shut down the temp is up and you need time to bring it down.
I had a 7 blade flex fan that worked great but gave me belt squeal no matter what I did. But the 7 blade flex fans are good for 8000 rpm

[leeklm]

"With the mechanical after you shut down the temp is up and you need time to bring it down"

Currently I have the luxury of my car always being at 180. It raises a little after shutdown, but right back at 180 after i start it up. It is a good problem to have, but I think I would have to TRY making this thing overheat!

The new non-thermal clutch is cheap enough, I might just try it and compare to the thermal clutch. My gut is telling me that I will spend more money on the electric setup than what I want, and will be less than thrilled with the end results.

After a fan blade or clutch puts a hole in my hood at 6k rpm, i many have a different outlook on it...

[AG]

I run a 7 blade flex in my streetcar with a 462 and the car will not go above 175 F on a 90 F day. I've raced it a few times with no issues. Had a Hayden severe duty clutch and factory 7 blade and the temp would rise when sitting in traffic.

[surfsama]

Originally Posted by leeklm

"With the mechanical after you shut down the temp is up and you need time to bring it down"

Currently I have the luxury of my car always being at 180. It raises a little after shutdown, but right back at 180 after i start it up. It is a good problem to have, but I think I would have to TRY making this thing overheat!

The new non-thermal clutch is cheap enough, I might just try it and compare to the thermal clutch. My gut is telling me that I will spend more money on the electric setup than what I want, and will be less than thrilled with the end results.

After a fan blade or clutch puts a hole in my hood at 6k rpm, i many have a different outlook on it...

Another option to consider is run an underdrive pulley on the crank. I'm running a 6.2 inch crank pulley and an 8 inch on the pump. My temps went up 5 degrees but at 6000 rpms my pump is only turning at 4700.

[leeklm]

Originally Posted by surfsama

Another option to consider is run an underdrive pulley on the crank. I'm running a 6.2 inch crank pulley and an 8 inch on the pump. My temps went up 5 degrees but at 6000 rpms my pump is only turning at 4700.

I found the 6" under drive crank pulley, but curious where you located an 8" pump pulley? My stock pulleys were 8" on the crank and around 6" on the water pump.

[KEN CROCIE]

loosen the belts. make a pass. if the vibes don't go away, look elsewhere.

[surfsama]

See number 5 on this chart.

[CROCIE JR]

Do what Ken Crocie said. Dont chase a problem that might not exist.

[CROCIE JR]

And just for info. Fan clutches are set up for how much fan resistance is applied. A HD thermo is never going to disengage with a 16" 4 blade. And a Chinese non thermo is never going to spin a 19" HD fan.

[leeklm]

Made a big change with the mechanical fan setup.. went to 6.25 crank pulley, an 8" pump pulley, and standard duty clutch fan. Made about 7 runs in mid-upper 80 degree and full sun. Car never got past 195, even while idling through pits after a run. Good news is absolutely no vibration.

I think I slowed things down a little too much, so will change back to the factory 8" crank pulley and see how it goes. At least now I can incrementally speed things up until I have ultimate cooling and no vibration.



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