Clutch Fan

[phil400]

I'd like to swap my original flex fan on my 78 to a heavy duty thermal clutch fan, been looking on line for those that have done which clutch fan part numbers and fan did you use Thanks?

[firebirdparts]

I don't know, I always used whatever was on the car.  I can probably read the number off one later.  Parts book says 547199 with A/C and that's a 7 blade fan. It is a Firebird only part, unfortunately.  They list it as 18-3/4" diameter.

I've bought a couple of fan clutches but I don't recall the brand.  Four Seasons I have heard of, but most of the ones that will fit otherwise were made by companies I've never heard of.  The only clutch fans I see now on RA are the slotted bolt hole kind that don't look right, but they do work.  There is an AC/Delco branded one still made.

[Wallington]

I don't know much about Pontiac specific parts, I have the parts manuals so can read the numbers but not easily found out which are which, which level of cooling, diameter, fan blades, some say, some don't.

My car has the Olds and the Heavy-Duty clutch equivalent was the Hayden 2747. Here's a flyer showing the 2747 and the newer slim 2947. Apparently other GM guys also use these units fairly often. Even with larger radiator, my stock setup still has plenty of clearance with the longer 2747.  There may be more units out there but this one is popular if need to compare pecs to others. Slotted mount and a few adapter bushes, Olds needed none. Mine already had the HD fan for A/C and HD cooling so no need to change. I see a few listed for Pontiac, AC or not, even for W72 or regular, whatever that changes.

https://www.haydenauto.com/media/5485/hayden_low-profile-fan-clutch-flyer.pdf

[phil400]

Ok Thanks

[apfstg]

On my ‘79 the olds fan diameter was bigger than  the Pontiac so watch the shroud opening

[Wallington]

I wasn't suggesting the fan swap, just the clutch assembly. Although many have swapped the shrouds back and forth like likely fit.

[Oldsschool79]

I used a Hayden 2705 , it has been working well even in very hot weather.

[phil400]

I used a Hayden 2705 , it has been working well even in very hot weather.

Which engine you running? Did you use a 6 or 7 blade fan?

[b_hill_86]

I ran a standard duty for years before I reinstalled AC. That was with a 5 blade fan. Never had any issues. When I reinstalled AC I switched to the heavy duty and a 7 blade fan. My only issue I chase is AC on and idling on a very hot day my temp starts creeping but only up to 205 or so. I haven’t given it a real good chance to get higher and it takes a while. Otherwise my engine runs around 185° on a hot day.

[phil400]

I ran a standard duty for years before I reinstalled AC. That was with a 5 blade fan. Never had any issues. When I reinstalled AC I switched to the heavy duty and a 7 blade fan. My only issue I chase is AC on and idling on a very hot day my temp starts creeping but only up to 205 or so. I haven’t given it a real good chance to get higher and it takes a while. Otherwise my engine runs around 185° on a hot day.

Good info Thanks

[Wallington]

Do you know what you have now, specs, part numbers?

[phil400]

It's the factory flex fan.

[Wallington]

So, no.

[jbanna]

Flex fans were not the original - I tried one for awhile, but didn't like the noise...I've had good luck with the stock fan clutch, but the car likes to run at 205...

[Wallington]

Assume that's what they meant, the stock type with alloy blades, not the fibreglass or completely alloy type.

[jbanna]

The flex fan is an aftermarket attempt to solve the problem with the fan clutches wearing out prematurely; however, my car never ran cooler with one, and the blades sounded like the propellers on an aircraft! I switched back to a fan clutch and a 7-bladed fan, and it works good...