Electric Fan placement opinions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Russell · 09-15-2005, 06:48 PM

Hey guys!

I'm setting my truck up with some electric fans, and I need some placement advice.

Basically, I need to know which side I should be putting the big fan on, driver's side, or passenger's side.

I am assuming that the hot coolant comes out of the top of the engine, into the rad and then is sucked back in the bottom side, so I'd figure that a guy would want to put the big fan on the driver's side where the inlet is, and put the little fan down by the pass side, where the coolant exits.

Sound good?

PS, the fans I am using are from two different chevy cars, one is from a 90s buick lesabre, with a 3.8, and the other is from what appears to be a mid 80s Nova. I think that chances are, I should be ok with just the big fan alone, as it is bigger, and has a steeper pitch to the blades than the stock fan was / had, but I want to put the little one on both for athetics, and for a backup if the big one fails for some reason. The little one is the same size as the 305 TPI Trans Am fans, and the big one is a little bit larger than the stock clutch fan.

Both fans have their own mini-shroud, but I intend to install the stock fan shroud (if it'll still clear the TPI MAF ducting) both to protect fingers, and to provide my place to store tools again, lol

Also would help with making sure that the air is directed properly at higher speeds, rather than just fluffing off wherever it wanted to go after it passed through the electric fan shroud.

MidnightBlues · 09-15-2005, 07:00 PM

Quote:

Originally Posted by Russell

I am assuming that the hot coolant comes out of the top of the engine, into the rad and then is sucked back in the bottom side,

Actually, I think it's the other way round.

Russell · 09-15-2005, 07:07 PM

I had the same nagging feeling, but then I remembered that the lower rad hose has a spring in it to keep it from collapsing from the suction of the water pump, so I am pretty sure it comes in the top, and out the bottom.

Could very well be wrong though!

*iceman7329* · 09-15-2005, 07:13 PM

Quote:

Originally Posted by MidnightBlues

Actually, I think it's the other way round.

Cause I had an intake on a 305 start leaking and it was shooting water out of the front of the engine in a good stream toward the front of the truck.

MidnightBlues · 09-15-2005, 07:17 PM

Yep,Russel, you're right. I just looked it up in my Haynes manual.
It's good you brought this up, cause I want to do the same mod as you this winter.
So I suppose the biggest fan should be at the hottest spot, that's on the top left of the rad.

Russell · 09-15-2005, 07:22 PM

Quote:

Originally Posted by iceman7329

Cause I had an intake on a 305 start leaking and it was shooting water out of the front of the engine in a good stream toward the front of the truck.

Gotta remember that the whole system is under close to 12 PSI of pressure, that means that any leaks in any direction will cause a pretty decent spray, lol

I'm gonna mount the fan by the inlet, and see how it does there

I just want to avoid making hot-spots the best I can.

ElGracho · 09-15-2005, 08:42 PM

The real answer to this is that it doesn't matter.

The area of the fan, the temperature of coolant and flow rates of both coolant and air are what determines how much heat will be rejected (cooled) by your radiator. If you place the fan on one side or the other, it will just stay hotter until it gets to where the fan is. Any gains by precise fan placement will be small.

piecesparts · 09-15-2005, 08:50 PM

The hot coolant goes to the radiator at the top of the motor (When the T/stat opens up). The principal is that heat goes up and cool goes down. So if you were to cool your motor off with natural circulation (what your motor does when it is turned off), then you would want the hot to go to the radiator at the top and go back into the motor at the bottom, to heat up again.

Russell · 09-15-2005, 10:03 PM

Sounds good, I got them both installed

I put the smaller of the two at the top of the rad so I could both make them look uniform until I get a full size shroud installed, and also to dissipate the rising heat.

I think they'll do just fine, I ran both fans at once, and they move a heck of a lot more air than the old mechanical fan used to! The big one definitely dims the lights and lowers the RPMs of the engine when it first turns on! Loud sucker, but I am pretty sure it'll do the job just fine!

bigarmzz · 09-15-2005, 10:41 PM

you might consider this as a cheap, but very effective electric fan setup

http://www.fordmuscle.com/archives/2...an/index.shtml

(i know, i'm using that "four letter word")

Russell · 09-16-2005, 12:10 AM

I actually stopped by the wrecking yard today, with the intent of getting one of those fans. I pulled one off, and was a bit dissapointed in the coverage it provided, so I decided to go with a pair of GM fans instead.

The big one is off a 3.8 powered Buick Lesabre, and the little one is off a little mid 80s appearing Nova (had no idea GM made a Nova during the mid 80s! It reminds me a bit of the little Charger that Dodge made during the mid 80s). Between the both of them, the entire rad is covered less a spot about 4 " x 3" at the bottom pass side of the rad. I was actually quite impressed with how easy they were to install as well, the 3.8 fan almost bolted right in, only needing one tie at the bottom middle edge of the fan, while the Nova fan also bolted in at the top, with one tie at the bottom. The 3.8 fan was spaced perfectly to sit right on the rad, it also has little flat spots so the fan shroud doesn't rub, I stuck an old core support bushing between the Nova fan and the rad, so it wouldn't rub.

After finishing the install, I don't believe I'll be able to install a factory fan shroud anymore, but thats not a big deal, cause this setup looks really good.

My new TPI chip also arrived today, so tommorow it'll just be a matter of pulling the upper intake one last time to check a few injectors, and fix a vac leak between the runners and lower intake, put the upper intake back together, and find some way to connect my MAF to the airbox that I mounted on the pass side fender. However, I'm thinking I may just get myself one of those cone filters, and plop it on the end instead, cause that airbox looks pretty restrictive. We'll see how the truck performs with it.

If all goes well, I should be able to pull the truck out of the shop under its own power tommorow

After that, I need to replace the wiring harness for the front clip, the harness that goes to the box, install my divorced transfercase, get shocks and driveshafts, then buckle down and get the body work done. I am starting to see the light at the end of the tunnel!

longhorn71 · 09-16-2005, 12:31 AM

Quote:

Originally Posted by ElGracho

The real answer to this is that it doesn't matter.

The area of the fan, the temperature of coolant and flow rates of both coolant and air are what determines how much heat will be rejected (cooled) by your radiator. If you place the fan on one side or the other, it will just stay hotter until it gets to where the fan is. Any gains by precise fan placement will be small.

I agree

**swervin ervin** · 09-16-2005, 10:28 AM

Russel,

you said you were going to install a shroud. You don't need one. The way you have your fans installed is the best way of doing it. Right up against the radiator. I have two Spal fans installed the same way. A shroud will only impead air flow when the fans are not running, as in normal driving conditions. A nicely built shroud looks very cool but is a total waste of time and money, IMO.

Russell · 09-16-2005, 11:19 AM

Ok, sounds good, I was thinking it'd help flow when a guy was going down the highway, but I couldn't think of how I was gonna mount it, seeing as my electric fans took the original shroud mount, lol

I guess we'll find out tonight if the big fan is up to keeping the small block cool

**swervin ervin** · 09-16-2005, 02:37 PM

Do you have them hooked to a temp switch so they only come on when needed or wired to stay on all the time? You really need the switch because you won't believe how much they are not needed. In the winter, mine never come on, anytime. In the summer, they will only come on if it's real hot and I get at a stop for awhile. Even then, in the summer they never come on in normal driving.

Good luck with them.

Mike

Russell · 09-16-2005, 05:03 PM

I've got the big one wired to my TPI ECM, and the little one is on a temp switch in the head of the engine and a manual switch by my towing brake controller. I mounted my tranny cooler right behind the small fan, so I would like to have the ability to turn that little fan on, and have it running at all times when I am towing a trailer to keep tranny temps down. When I am not towing, it'd just be there to act as a complimentary fan to the big one if it is not able to keep up on a 100 degree day stuck in traffic

454HO · 09-16-2005, 05:45 PM

Your install looks real good. Do you happen to know the diameter of those fans? I also like the way you wired them up. But I am curious what thermostat temp you plan to run, what temp does your TPI ECM turn the big fan on, and what temp your thermal switch turns the small fan on? Oh, and do you have a temp gauge in the transmission pan?

Russell · 09-16-2005, 11:18 PM

The big fan is a 16" fan, and the little one is a 12" fan. The thermostat is a 195 F unit, right about where the TPI likes to run. The ECM is programmed to turn the fans on at 205 F, and off at 185 F, if I remember correctly. The little thermal switch is suppost to turn the fans on at 220 F, and off at 185. I currently don't have a tranny temp switch, though I think I probally will install one sooner than later. Just need to find a nice place to put one

09-15-2005, 06:48 PM	#1
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Electric Fan placement opinions Hey guys! I'm setting my truck up with some electric fans, and I need some placement advice. Basically, I need to know which side I should be putting the big fan on, driver's side, or passenger's side. I am assuming that the hot coolant comes out of the top of the engine, into the rad and then is sucked back in the bottom side, so I'd figure that a guy would want to put the big fan on the driver's side where the inlet is, and put the little fan down by the pass side, where the coolant exits. Sound good? PS, the fans I am using are from two different chevy cars, one is from a 90s buick lesabre, with a 3.8, and the other is from what appears to be a mid 80s Nova. I think that chances are, I should be ok with just the big fan alone, as it is bigger, and has a steeper pitch to the blades than the stock fan was / had, but I want to put the little one on both for athetics, and for a backup if the big one fails for some reason. The little one is the same size as the 305 TPI Trans Am fans, and the big one is a little bit larger than the stock clutch fan. Both fans have their own mini-shroud, but I intend to install the stock fan shroud (if it'll still clear the TPI MAF ducting) both to protect fingers, and to provide my place to store tools again, lol Also would help with making sure that the air is directed properly at higher speeds, rather than just fluffing off wherever it wanted to go after it passed through the electric fan shroud. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

09-15-2005, 07:07 PM	#3
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	I had the same nagging feeling, but then I remembered that the lower rad hose has a spring in it to keep it from collapsing from the suction of the water pump, so I am pretty sure it comes in the top, and out the bottom. Could very well be wrong though! __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

09-15-2005, 07:17 PM	#5
MidnightBlues Registered User Join Date: Oct 2002 Location: The Netherlands Posts: 118	Yep,Russel, you're right. I just looked it up in my Haynes manual. It's good you brought this up, cause I want to do the same mod as you this winter. So I suppose the biggest fan should be at the hottest spot, that's on the top left of the rad. __________________ Andre 1984 C10 SWB, 350/700R4 Last edited by MidnightBlues; 09-15-2005 at 07:18 PM.

09-15-2005, 08:42 PM	#7
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,553	The real answer to this is that it doesn't matter. The area of the fan, the temperature of coolant and flow rates of both coolant and air are what determines how much heat will be rejected (cooled) by your radiator. If you place the fan on one side or the other, it will just stay hotter until it gets to where the fan is. Any gains by precise fan placement will be small. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

09-15-2005, 10:03 PM	#9
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Sounds good, I got them both installed I put the smaller of the two at the top of the rad so I could both make them look uniform until I get a full size shroud installed, and also to dissipate the rising heat. I think they'll do just fine, I ran both fans at once, and they move a heck of a lot more air than the old mechanical fan used to! The big one definitely dims the lights and lowers the RPMs of the engine when it first turns on! Loud sucker, but I am pretty sure it'll do the job just fine! __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

09-15-2005, 08:50 PM	#8
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	The hot coolant goes to the radiator at the top of the motor (When the T/stat opens up). The principal is that heat goes up and cool goes down. So if you were to cool your motor off with natural circulation (what your motor does when it is turned off), then you would want the hot to go to the radiator at the top and go back into the motor at the bottom, to heat up again.

09-15-2005, 10:41 PM	#10
bigarmzz Registered User Join Date: Sep 2004 Location: Elkins, West Virginia Posts: 2,542	you might consider this as a cheap, but very effective electric fan setup http://www.fordmuscle.com/archives/2...an/index.shtml (i know, i'm using that "four letter word") __________________ 1987 350 TBI lowered 5/7

09-16-2005, 12:10 AM	#11
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	I actually stopped by the wrecking yard today, with the intent of getting one of those fans. I pulled one off, and was a bit dissapointed in the coverage it provided, so I decided to go with a pair of GM fans instead. The big one is off a 3.8 powered Buick Lesabre, and the little one is off a little mid 80s appearing Nova (had no idea GM made a Nova during the mid 80s! It reminds me a bit of the little Charger that Dodge made during the mid 80s). Between the both of them, the entire rad is covered less a spot about 4 " x 3" at the bottom pass side of the rad. I was actually quite impressed with how easy they were to install as well, the 3.8 fan almost bolted right in, only needing one tie at the bottom middle edge of the fan, while the Nova fan also bolted in at the top, with one tie at the bottom. The 3.8 fan was spaced perfectly to sit right on the rad, it also has little flat spots so the fan shroud doesn't rub, I stuck an old core support bushing between the Nova fan and the rad, so it wouldn't rub. After finishing the install, I don't believe I'll be able to install a factory fan shroud anymore, but thats not a big deal, cause this setup looks really good. My new TPI chip also arrived today, so tommorow it'll just be a matter of pulling the upper intake one last time to check a few injectors, and fix a vac leak between the runners and lower intake, put the upper intake back together, and find some way to connect my MAF to the airbox that I mounted on the pass side fender. However, I'm thinking I may just get myself one of those cone filters, and plop it on the end instead, cause that airbox looks pretty restrictive. We'll see how the truck performs with it. If all goes well, I should be able to pull the truck out of the shop under its own power tommorow After that, I need to replace the wiring harness for the front clip, the harness that goes to the box, install my divorced transfercase, get shocks and driveshafts, then buckle down and get the body work done. I am starting to see the light at the end of the tunnel! Attached Images __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap) Last edited by Russell; 09-16-2005 at 12:12 AM.

09-16-2005, 10:28 AM	#13
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Russel, you said you were going to install a shroud. You don't need one. The way you have your fans installed is the best way of doing it. Right up against the radiator. I have two Spal fans installed the same way. A shroud will only impead air flow when the fans are not running, as in normal driving conditions. A nicely built shroud looks very cool but is a total waste of time and money, IMO. __________________ Mike 1985 Chevy C-10

09-16-2005, 11:19 AM	#14
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Ok, sounds good, I was thinking it'd help flow when a guy was going down the highway, but I couldn't think of how I was gonna mount it, seeing as my electric fans took the original shroud mount, lol I guess we'll find out tonight if the big fan is up to keeping the small block cool __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

09-16-2005, 02:37 PM	#15
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Do you have them hooked to a temp switch so they only come on when needed or wired to stay on all the time? You really need the switch because you won't believe how much they are not needed. In the winter, mine never come on, anytime. In the summer, they will only come on if it's real hot and I get at a stop for awhile. Even then, in the summer they never come on in normal driving. Good luck with them. Mike

09-16-2005, 05:03 PM	#16
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	I've got the big one wired to my TPI ECM, and the little one is on a temp switch in the head of the engine and a manual switch by my towing brake controller. I mounted my tranny cooler right behind the small fan, so I would like to have the ability to turn that little fan on, and have it running at all times when I am towing a trailer to keep tranny temps down. When I am not towing, it'd just be there to act as a complimentary fan to the big one if it is not able to keep up on a 100 degree day stuck in traffic __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap) Last edited by Russell; 09-16-2005 at 05:11 PM.

09-16-2005, 05:45 PM	#17
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,223	Your install looks real good. Do you happen to know the diameter of those fans? I also like the way you wired them up. But I am curious what thermostat temp you plan to run, what temp does your TPI ECM turn the big fan on, and what temp your thermal switch turns the small fan on? Oh, and do you have a temp gauge in the transmission pan? __________________ - Greg

09-16-2005, 11:18 PM	#18
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	The big fan is a 16" fan, and the little one is a 12" fan. The thermostat is a 195 F unit, right about where the TPI likes to run. The ECM is programmed to turn the fans on at 205 F, and off at 185 F, if I remember correctly. The little thermal switch is suppost to turn the fans on at 220 F, and off at 185. I currently don't have a tranny temp switch, though I think I probally will install one sooner than later. Just need to find a nice place to put one __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)



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