vmathy

Just overheated waiting in line to register at a local show. A previous owner put a flex fan on this 455 in a 71 cutlass. I think this is my problem. What is the proper or best fan for me to change to? By the way outside temp was 100 degrees when this hapened.

Lady72nRob71

Please define overheating - in degrees or did the light come on?
Shroud in place? Is this an AC car? If so,then maybe it is time to return to the stock clutch fan....

71 Cutlass

Also could just be that you need a new radiator cap. Start with easiest first then graduate to hardest.

joe_padavano

Flex fans are awful. Get a proper clutch fan.

nj_cutlass72

i have the stock fan that constantly runs and sometimes cant hear the engine, i was told it takes some hp as well. what should I replace with?

Lady72nRob71

You mean you hear a constant roaring sound even when it is running cool? If so, the clutch (if equipped) may not be disengaging. Provide us with some more info (year, model, A/C or not, when you hear it and not) so we can help..

nj_cutlass72

its a 72 cutlass, w AC, the fan runs hot or cold, i hear the fan constantly.. so i want to disengage if not necessary to run. whats the fix?

Lady72nRob71

Sounds like your fan clutch is not disengaging - replace it.

Normally it should engage for a few minutes after a cold startup but after then should disengage. It should then engage again when the temp. in front of it exceeds 195* and disengage when it drops below that.

Run to Rund

A five, six, or seven blade fan with well operating clutch is probably best. If you want to try a good flex fan, they were OEM on some Buicks, etc. They are much different from the aftermarket junk that cools about as well as having nothing on the hub. I have several Buick type fans that I have been hoarding for 30+ years and will never use. I'd sell them for not much more than shipping, but that could be expensive these days.

75cutty455

Why not go with an electric fan and gain a few HP? Any objections anyone? Pros, Cons?

Fakser

Electric is nice...lets see some months back someone posted a cool thread about a junkyard fan conversion. Joe P you know where that one is?

507OLDS

Converting to electric fans will not always show a benefit.I coneverted to twin pullers for no reason.I just felt like doing it. My previous set-up was a factory Harrison radiator,with factory shroud,and a $15.00 Flex-a-lite nylon 6-blade fixed(no clutch)fan.I NEVER had any issues with this set-up,no matter what I was doing with the car.Even on the hottest/humid days,it never got above 185*,even sitting in city traffic or a parade.
A few years back I decided to swap the radiator for an aluminum Griffin,& install twin Flex-a-lite pullers.It runs exactly the same,185*. I didn't shed any weight either.What I lost in radiator weight,I gained back with the electric fan assembly.

Lady72nRob71

Not to mention the alternator usually requires an upgrade to a higher output unit.
Not a lot to gain on a street car going electric.

507OLDS

I already had the better alternator on the car anyway.I literally had these parts laying on a shelf in my garage,and I had some free time one afternoon,so I swapped it all over.It's the only way to find out.My ET's weren't any different either.I plan on running an electric water pump on my 517 when it's done,so the fans & radiator will stay the way they are.I just know I don't need to go out of my way to do this on another car.

nj_cutlass72

so the fan I have is a running fan, no matter hot and cold... what I want to know is how does the clutch fan work? how does it know to kick in... and where do I get one? few tid bits about installation would be great! thx

Lee_A

Until a few years ago, I had a '67 Firebird with a 469" Pontiac, street/strip mid-11's at the time. I had a few hundred passes on the car, so I had a good amount of data on the car. It had a non-clutched flex-fan and a factory waterpump (stock pulleys), and I replaced those with a CSR waterpump and a Flex-a-lite Black Magic shrouded fan.

With the electric fan and pump, my mph increased 1.1 and my e.t. dropped .09 - and I could cool the motor in under 5 minutes between runs, and the motor ran cooler all around (but MUCH more cooler in low-speed and stop-and-go traffic).

Lee

Lady72nRob71

The clutch monitors air temperature off the radiator with both an aluminum finned body and a bimetallic spring (like a thermostat). If below 150* it kinda freewheels. Between 150-190*, it will engage via fluid coupling, having no more than 25% slippage. The result is a large volume of air being moved until the temp drops enough for the clutch disengages. The clutches can be found at most auto parts stores. Installation is based on your year and model car and if it came with a clutch, has A/C, etc.