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Electric fan questions
https://slantsix.org/forum/viewtopic.php?t=13495		 Page 1 of 3
Author:  textoad [ Tue Jun 28, 2005 9:37 am ]
Post subject:  Electric fan questions
74 Scamp with factory air. We're going the electric fan route and I have a few questions.

It appears we need about 1800 to 2000 CFM from what I have read. A company called Hayden sells fans at the local auto parts store. Their catalog recommends 2 1250CFM fans for the Slant Six. However two of their recommended 14 in dia electric fans won't fit across the radiator without lots of overhang. So I am thinking of 1 - 14 inch 1250 fan and another 10 inch 600 CFM fan mounted diagaonally across the radiator. Does this sound reasonable?

Also, there are options on senors. Should I go with a coolant sensor or air sensor. The coolant sensor could be inserted in a port in the upper radiator tank. The air sensor would go in the radiator fins. Which would be best?

Also should the fans be switched on via a relay activated by The AC compressor on?

And should it be on only when the ignition is on?

And obviously they should come on based on the temp sensor.

In other words do I need to do a little rela/diode Or function to get all these conditions.

I would imagine I would want the fans on when the AC is on regardless of the temp sensor therefore effectively overiding the temp sensor. Also I when AC is off I would want the fans on based on ignition on and temp sensor conditions.

Am I making too much of this?

Another question is the alternator capacity. On a 74 Slant Six I'm not sure about the alternator capacity. I think it will handle the extra load but I am not sure. The only info I can find on the Hayden 3690 fan is no more than 16 amps. If I use the 10 inch and 14 inch together I'm looking at possibly 32 amps maximum. Not sure if that is at startup only or what. Also should I consider unsually high load situations such as starting the car with AC on and other accessories such as radio, headlights etc. I could disable the fans during startup only to limit the load if you guys think it's necessary.

Also I live in Tucson where worst case temps approach 120 periodically during the summer.

Thanks in advance.
Author:  SlantSixDan [ Tue Jun 28, 2005 10:00 am ]
Post subject:  Re: Electric fan questions
Quote:
It appears we need about 1800 to 2000 CFM from what I have read. A company called Hayden sells fans at the local auto parts store. Their catalog recommends 2 1250CFM fans for the Slant Six. However two of their recommended 14 in dia electric fans won't fit across the radiator without lots of overhang. So I am thinking of 1 - 14 inch 1250 fan and another 10 inch 600 CFM fan mounted diagaonally across the radiator. Does this sound reasonable?
Not the cleanest solution. Look at other companies' products—pay special attention to Flex-a-Lite's line, which is much more complete than Hayden's. And for that matter, there's no need to spend for a new fan. For $10 to $30, you can get a fan off a 3.8-litre GM front-drive car (there are TONS of these in wrecking yards) that'll be about the right size to cover the radiator in your A-body, and moves tons of air. Even if you want new for reliability, you can get the GM fan and easily/cheaply replace the motor with a new one.
Quote:
Should I go with a coolant sensor or air sensor.
Coolant. Much easier to dial in to work the way you want.
Quote:
Also should the fans be switched on via a relay activated by The AC compressor on?
Definitely YES. You can use a dual-output relay (e.g. Bosch 0 332 019 109 or 0 332 019 151; we sell several hundred of these per month); one to feed your A/C compressor clutch and the other to override the thermo control and turn on the rad fan. This will have the added benefit of taking the high-current clutch load off your A/C mode selector switch in the passenger compartment, which will greatly extend the switch's life.
Quote:
And should it be on only when the ignition is on?
Given that you live in a hot area and have a carbureted car, you may want to set up the fan control circuit such that the fan runs for a minute or two or three after shutdown. This can really help cool the engine compartment and reduce vapour-related hot start/hot idle problems. If you do this, make sure you use GOOD QUALITY relays...cruddy 3rd-worldy ones can stick closed and drain your battery dry via the rad fan.
Quote:
In other words do I need to do a little rela/diode Or function to get all these conditions.
Flex-a-lite sells several different electric fan controllers, ranging from plain ol' simple to really fancy. They are all universal; they don't know or care who made the fan they're connected to, or whether you bought it at a parts store or a wrecking yard.
Quote:
Am I making too much of this?
No, you're thinking it through in advance, which means fewer problems to fix and messes to clean up later.
Quote:
Another question is the alternator capacity. On a 74 Slant Six I'm not sure about the alternator capacity.
From the factory? 35A to 65A depending on vehicle equipment and original-order specification. Now, 31 years later? Who knows?
Quote:
I think it will handle the extra load but I am not sure.
If it's in good shape, it probably will; the bigger question is whether it'll keep up with demand at idle and low engine speeds, which is where the '60s-'70s Chrysler charging systems tend to be relatively weak.

It's not at all difficult to retrofit a later ('80s) Chrysler, Bosch or Nippondenso 40/90 alternator that will supply all the current you need at idle without breaking a sweat. The upper bracket is the same; you need the lower bracket from a '76-up slant-6 with the sheetmetal (rather than cast iron) lower alternator bracket. This spaces the bottom of the alternator farther out from the head, which is what's necessary to mount the later alternator. The alternator itself comes from an '89 Diplomat/Gran Fury or an '89-'93 Dodge truck or van.

Whatever control system you wind up with, be sure to include adequate and correctly-calculated circuit protection (fuses/circuit breakers) everywhere you take off live power (fan power lead, AC clutch/fan relay power lead)...and carry spare fuses in case your calculation was off!
Author:  textoad [ Tue Jun 28, 2005 12:18 pm ]
Post subject: 
Thanks Dan. I looked at a few later model GM's for radiator fans at lunch today. I looked at a Caddy front drive V8 and a Buick Park Avenue 3.8l. Both had large 16 inch fans but they looked too deep. I'll have to make some careful measurements. I only have about 4 inches between the radiator and the pully on the water pump. I could possibly offset it but I'll have to look.
Author:  emsvitil [ Tue Jun 28, 2005 12:33 pm ]
Post subject: 
Summit has a 16" that's rated at 2010CFM....

It's not a deep fan
Author:  toplesslant [ Tue Jun 28, 2005 3:42 pm ]
Post subject: 
when I looked at getting a fan and radiator from Summit, which I bought and was delivered I found that the fan wouldnt fit with the aftermarket OR the stock radiator so be careful as to the thickness of the fan :wink:
Author:  70valiant [ Tue Jun 28, 2005 6:10 pm ]
Post subject: 
When I was using a radiator from an aspen in my 70 valiant I could just barely get the fan from a Culess Cierra GT to fit. It had to over hang the passenger side of the rad about 2 inches and about 4 inches of the drivers side of the rad wasn't covered by the shroud. it cooled beautifully though. Once I replaced the rad with a high capacity OEM V8 unit the fan would no longer fit. I went with a 16" pusher from a mercedes out of a junk yard. To controle the fan I bought an adjustable thermostatic switch at National auto for $23. It has 2 wires, one goes to a 20 amp or greater switched fuse on the fuse block, the other goes to the + wire on the fan. It has a coil attached to the sensor that you attach to the outside of the rad. It does the job for me. I haven't had any alternator problems yet.
Author:  Dart270 [ Tue Jun 28, 2005 9:20 pm ]
Post subject: 
I have used 16" flex-a-lite fans on stock radiators with great success, but not with AC.

Lately, my philosophy has been to put in a better radiator (aluminum, 2" thick) and a small fan (12" is fine). This has kept the cars cooler and allowed me to run the fan very infrequently, pretty much only when idling for more than 5 min in hot weather.

Afcoracing.com makes a very nice universal "Chevy" style (pass lower hose, driver upper hose) rad that weighs about 14lbs and costs $180, and has 50-100% more cooling capacity than a factory Dart rad, even a 3-core.

Something to consider...

Lou
Author:  moparDuster [ Tue Jun 28, 2005 10:57 pm ]
Post subject: 
i've been thinking of adding an electric fan. but was wondering is a pusher better then a puller? whats the best one i can find in a junkyard
Author:  Pierre [ Tue Jun 28, 2005 11:01 pm ]
Post subject: 
Lou those afco radiators look nice but the cheaper $180 versions don't have provisions for trans cooling.... the ones with heat exhcangers (fancy name for trans cooler, right?) are $320.
Author:  emsvitil [ Wed Jun 29, 2005 12:03 am ]
Post subject: 
Quote:
i've been thinking of adding an electric fan. but was wondering is a pusher better then a puller? whats the best one i can find in a junkyard

Puller is more efficient.
Author:  Charrlie_S [ Wed Jun 29, 2005 3:49 am ]
Post subject: 
Quote:
Quote:
i've been thinking of adding an electric fan. but was wondering is a pusher better then a puller? whats the best one i can find in a junkyard

Puller is more efficient.
Explain, please. I would think 1500 cfm is 1500 cfm, whether it is a pusher or puller.
Author:  Dart270 [ Wed Jun 29, 2005 4:58 am ]
Post subject: 
Good point on the trans cooler. On my mostly track car, I just run an external cooler only, mounted under the car.

Lou
Author:  emsvitil [ Wed Jun 29, 2005 9:27 am ]
Post subject:  Puller vs Pusher
I don't get it myself, but various sites always state that a puller is more efficient.

From http://www.perma-cool.com/faq/efans.html#installed

What is more efficient a "pusher" or "puller" electric fan?

A puller fan is more efficient. A pusher fan is generally only 80% as efficient as a puller fan.
Author:  SlantSixDan [ Wed Jun 29, 2005 10:05 am ]
Post subject: 
I get a leetle suspicious when I see one-to-three sentence "answers" like this perma-cool outfit supplies, without any explanation or references. Another similar "answer" from that same site states, in its entirety: "A four cylinder engine requires 1600 cfm; a six cylinder engine requires 2,000 cfm, a small V-8 engine requires 3,000 cfm and large V-8 engines require 4500+ cfm.".

Um, horsepuckey.

There are MANY factors that affect how much air you need to pull with the cooling fan. Number of cylinders is one of those factors, but it most certainly isn't the only one, and it most certainly isn't the primary one. An '04 Stratus R/T with A/C and a turbo 2.4 litre 4-cylinder engine with cramped engine bay breathing needs—and has—a lot more fan than a '61 Dart with 3-on-the-tree and a 318 V8 engine, no A/C, with lots of engine bay breathing.
Author:  argentina-slantsixer [ Wed Jun 29, 2005 2:04 pm ]
Post subject: 
I'm running twin small fans in mine. They're from a renault 18 2.2 litres with A/C and tons of heating up devices (poor engine bay breathign too) I'll take some pix and post them later. I used single 70 amp relay (I had it laying around) and a tricky setup for the thermoswitch. I have a 3 points toggle switch wired thermo control @ center, sides are 1 straight groud (permanently on) and the other goes to the relay. Used no fuse (so sue me) if I leave it on "Auto" it starts and stops when the thermo feels like working. After cutting ignition off, since I wired the relay permanently hot, sometimes it works for a li'l while (2, 3 minutes, exceptionally has worked 5-7 minutes when outside temp was 40+Celsius and I parked after a hard drive) and sometimes not (when it's winter like now). Never had again any warm startup issues.

Hey you, electrogeek dan, do you know CFM rate for those fans? (this Q will be valid after I post pix)

Take care
Juan
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