Fan Clutch or Not?

Posted By: bobs66440

Fan Clutch or Not? - 02/28/12 03:39 PM

I have been running a 15" fixed fan with no shroud up until now with no problems. Looking ahead a little with my 440 build and not knowing what to expect, I just picked up an 18" fan to help cooling a bit. I was wondering about a fan clutch, whether to use one or not. I understand the operation theory, but is it necessary?

Posted By: babarracuda

Re: Fan Clutch or Not? - 02/28/12 03:47 PM

A fan clutch is only necessary if you mind a loud!!! fan or 1-2 MPG less.

Posted By: torkrules

Re: Fan Clutch or Not? - 02/28/12 05:36 PM

Quote:

I have been running a 15" fixed fan with no shroud up until now with no problems. Looking ahead a little with my 440 build and not knowing what to expect, I just picked up an 18" fan to help cooling a bit. I was wondering about a fan clutch, whether to use one or not. I understand the operation theory, but is it necessary?

Using one depends on a lot of things. Some of the aftermarket aluminum rads that have thick cores, make it difficult to find a short enough clutch that will fit. The five blade mopar one works fine if it will fit, but you will need a large rad as I have found they don't move enough air at idle for some combos.

This stuff all has to be done as a package. Usually the pully on the water pump is a little smaller than the crank pully to give it a little over drive speed. The stock set up using a large 18" or bigger fan with 6 or 7 blades. The smaller pulley helps with cooling and not performance, and the opposite is true.

I would start by looking at your application (lots of idling, hot weather driving-large fan, big rad, shroud, small waterpump pulley-short trips, limited use, street strip car-larger pulley, mopar fan clutch/flex fan)
Compression plays a big roll in this as does timing.

I run a solid 16" fan with a shroud and a 22" aluminum rad, 1:1 pulleys in a Road Runner with a 650HP 472 Hemi.) It's a street only car and in the heat it sits around 180-185, however if it idles in the heat longer than 15 minutes it will start to heat up, but it cools right back down once it's moving

Posted By: Mr.Yuck

Re: Fan Clutch or Not? - 02/28/12 06:09 PM

I use a Summit 18.5 plastic fan w/ a spacer. I've used a few. they are very light, won't cut your fingers up and cool very well. Oh and they are CHEAP!

Posted By: Mr.Yuck

Re: Fan Clutch or Not? - 02/28/12 06:13 PM

http://www.summitracing.com/parts/SUM-G4948/

this one I think...

Posted By: DAYCLONA

Re: Fan Clutch or Not? - 02/28/12 06:17 PM

I always prefer a fixed factory HD cooling fan,....and GET a shroud, it makes a world of a difference, space the fan so that at least 50-75% of the blades are tucked inside it for a good suction effect, try to maintain 1" or more away from the radiator itself, as even fixed plades flex under extreme RPM, as well as driveline shift, which might cause the fan to chew into the radiator....

Posted By: can.al

Re: Fan Clutch or Not? - 02/28/12 10:00 PM

..good info on hayden's web site
.. standard fan clutches spin at about 70%
of the pulley speed so some engines will run a little
hot at idle,and when they fail you're in trouble
..i like a fixed or even a flex style.

Posted By: forphorty

Re: Fan Clutch or Not? - 02/29/12 01:44 AM

http://www.carnut.com/ramblin/dyno.html http://forums.corvetteforum.com/c3-tech-performance/644713-flex-fan-better-than-a-clutch-fan.html

Posted By: bobs66440

Re: Fan Clutch or Not? - 02/29/12 01:53 AM

Thanks for the info. I think I'm going to stick with a fixed fan. I don't need cooling issues at idle and I've heard about the problem with them failing and overheating an engine. And I'm going to get a shroud. I just don't know what size radiator I'm going to end up with. I'm leaning toward the Champion 26". I'm using a 22" now and it works well, but it may prove inadequate for the new mill.

Quote:

I use a Summit 18.5 plastic fan w/ a spacer. I've used a few. they are very light, won't cut your fingers up and cool very well. Oh and they are CHEAP!

Funny you should mention that. Just last week I bought a 18" Flexalite plastic fan exactly like the Summit one. I used one on my hot rod and it did move some serious air! And as you say, it's very light...weighs almost nothing and is good up to 8000rpm.

Posted By: bobs66440

Re: Fan Clutch or Not? - 02/29/12 02:06 AM

Quote:

http://www.carnut.com/ramblin/dyno.html http://forums.corvetteforum.com/c3-tech-performance/644713-flex-fan-better-than-a-clutch-fan.html

Good info, thanks. I love that carnut site BTW.

Posted By: Mr.Yuck

Re: Fan Clutch or Not? - 02/29/12 02:25 AM

Bob i have a 26" 2 core aluminum rad and this thing doesn't get over 190* when it does as soon as I move it drops to 170*. The 67 S/C'd 440 was the same way, except it had a 4 core 26" rad.