Author Topic: Clutch Fan (Read 3016 times)

phil400 · « **on:** February 24, 2024, 11:13:39 AM »

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 · « **Reply #1 on:** February 24, 2024, 11:10:31 PM »

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 · « **Reply #2 on:** February 25, 2024, 05:13:49 AM »

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 · « **Reply #3 on:** February 25, 2024, 06:37:30 AM »

Ok Thanks

apfstg · « **Reply #4 on:** February 25, 2024, 08:45:33 AM »

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

« **Reply #4 on:** February 25, 2024, 08:45:33 AM »

Wallington · « **Reply #5 on:** February 25, 2024, 09:36:37 AM »

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

Oldsschool79 · « **Reply #6 on:** February 26, 2024, 04:49:57 AM »

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

phil400 · « **Reply #7 on:** February 26, 2024, 05:58:19 AM »

Quote from: Oldsschool79 on February 26, 2024, 04:49:57 AM

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 · « **Reply #8 on:** February 26, 2024, 08:22:06 AM »

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 · « **Reply #9 on:** February 26, 2024, 06:02:32 PM »

Quote from: b_hill_86 on February 26, 2024, 08:22:06 AM

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 · « **Reply #10 on:** February 26, 2024, 09:21:02 PM »

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

phil400 · « **Reply #11 on:** February 27, 2024, 05:26:38 AM »

It's the factory flex fan.

Wallington · « **Reply #12 on:** February 27, 2024, 08:24:59 AM »

So, no.

jbanna · « **Reply #13 on:** April 30, 2024, 11:27:28 PM »

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 · « **Reply #14 on:** May 01, 2024, 01:42:18 AM »

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

« **Reply #14 on:** May 01, 2024, 01:42:18 AM »

jbanna · « **Reply #15 on:** May 01, 2024, 02:10:41 AM »

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...

nUcLeArEnVoY · « **Reply #16 on:** May 03, 2024, 11:20:12 AM »

A standard duty clutch fan was what was equipped from the factory, which would be a Hayden 2705. This was even for AC cars.

Most owners upgrade to the Heavy Duty 2747, which is JUST barely applicable for the 18.5-19" Pontiac 400 or Olds 403 fans. This is what I use and it cools very well.

Still, others overkill and use the Severe Duty 2797. The issue with using this clutch is that it is meant for fans with a much larger pitch than any factory fan, and as a result it is pretty much engaged 100% of the time. This overcools the motor as well as robs engine power due to how stiff it is.

phil400 · « **Reply #17 on:** May 24, 2024, 06:34:58 PM »

If any is interested, or has a master parts catalog I found 2 part numbers on the original fan off the car, #526075 also found 916 452 078,

Also have another factory flex fan I took off YP350 block has same part number 526 075 and second number is 916 452 D77

Decided to stick with what's on the car.

« **Reply #17 on:** May 24, 2024, 06:34:58 PM »

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Author Topic: Clutch Fan (Read 3016 times)