CUTLASS GM Parts Of The Moment- A Lame Tutorial- 307 Fan Clutches (1985)

[69hurstolds]

Fan clutches. Not many people notice or even care about them. Except when they don't work. We can get into all the specifics on how they work, etc., but I want to keep this short. Effectively when things heat up, the fan clutch moves fluid chambers to "solidify" the fan into more of a lockup operation so the fan works to move more air. As the coolant heat drops across the radiator, the fan gets looser and slips more, and doesn't work as hard.

Anyway, there are TWO versions of the fan clutch that were used on VIN Y/9 engines across Oldses lineup for 1985. The OJ coded fan clutch and the OL coded fan clutch. Looking backwards, the OJ was used on a bunch of V8 applications in very late 70s up through sometime in January/February of 1985. Exactly when that happened, I don't know. Then the OL code took its place. Now, the parts book shows the latest number of 22049774 which covers OJ or OL in the nomenclature. The OJ itself came under GM p/n 559729.

Here's an OJ.

And the NOS OL one. My gray 85 442 came with an OJ, but my black 85 442 came with an OL.

 

[john87442]

Good information, would I be able to use my stock fan and clutch setup on the olds 350 I’m putting in my 87 442? My builder said I should get a six blade fan but didn’t elaborate why.
I am installing a cold case radiator and wanted to use the factory shroud.

 

[69hurstolds]

Yes. Your stock fan and clutch should be no issue on your 350. EVERYTHING as far as your pulleys and belt-driven accessories from your 307 should bolt up to the 350. Just have to make sure you have the studs in the right places on the heads as needed.

The number of fan blades don't matter too much as long as you have the ability to move a LOT of air when needed at low speeds and stop lights, etc. The pitch and diameter is what makes that possible, normally. Obviously you don't want a 2 blade propeller, but the stock 307 fan works just fine with the clutch. 260s to 350s used the same fan clutch in the late 70s early 80s, so it make sense they should work just fine.

But make sure the fan's not bent. Bent stuff on a rotating fan is bad for the clutch. It can put too much side stress on the shaft as it rotates and could damage the seals, having the fluid leak out and even at partial operation, you may not notice the fan slowing down then wonder why you're overheating and thinking the fan clutch is still working right. Always inspect for dirt build up sticking to the leaking fluid around the clutch shaft because that's usually your first warning sign. GM recommends replacing a bent fan, and not to straighten it. Which is fine if you have access to new fans, but you'd be hard pressed to find a new one now.

 

[Supercharged111]

The number of fan blades don't matter too much as long as you have the ability to move a LOT of air when needed at low speeds and stop lights, etc. The pitch and diameter is what makes that possible, normally.

I wouldn't downplay blade count. Clutches are matched to fans and the amount of resistance they have, all else being equal this would be dictated by pitch. But more blades also = more resistance, so you could end up with a fan that runs too often or not often enough. I kinda doubt that's the case here, but still. Did the changeover in clutches correspond with an updated fan design?

 

[69hurstolds]

I wouldn't downplay blade count. Clutches are matched to fans and the amount of resistance they have, all else being equal this would be dictated by pitch. But more blades also = more resistance, so you could end up with a fan that runs too often or not often enough. I kinda doubt that's the case here, but still. Did the changeover in clutches correspond with an updated fan design?

No. No changes on fan part number. Still the same old lopsided 19" 5-blade stock fan (The reason is they're lopsided for noise reduction). It's very possible they simply changed vendors, changing the code and part number. But I don't know.

Nobody's downplaying blade counts. Put on a 6-blade if you wish, but it won't be an Olds V8 fan. I'm sure GM made a 6-blade fan for something, just not a G-body Olds V8 that I'm aware of. Likely smaller diameter, too, which may or may not affect flows. Seems to me Chevies used those in the 70s. Heck, while you're at it, go find a diesel and get the 7-blade fan. They're 19" across, too. Note too, non-AC G-body cars normally use a 19" 4 blade X fan and a spacer. Looks kinda cool, actually.

But I digress. Blade count is only important to a degree, as stated. It depends on the physical properties of the setup, the fan, and the clutch (if used). It's just that to throw an arbitrary "get a 6 blade fan" without knowing how the cooling system air stream is set up is painting with a wide brush. Why not get an electric fan setup? When it comes to fans, more (or less) blades isn't always guaranteed to be better. Besides, clutches are supposed to be dictated whether "on" or "off" by sensing air temperature coming through the radiator. The clutch honestly doesn't care how many blades the fan has. It's either going to lock up or it won't.

A 5-blade stock fan with a factory calibrated fan clutch is perfectly suited for street use on a warmed over 350 and anybody is welcome to try and convince me for a mild street car you'd need anything different. If you change stuff up, or make a ton of power, you may need something different like electric fans, bigger rad, etc. Then it's on you, as you're taking over design engineering duties for your custom setup. Would a 6-blade fan work better? I dunno. It might. It might not. I wouldn't worry about it until you know for sure the stock setup isn't working well enough. I'm not one for spending money on new parts I don't have to, until I have to.

 

[john87442]

Thanks for everyone’s input and suggestions. I am going to use the setup I had on my 307 and see how it does before I go changing anything else. I did get a cold case radiator for it but that’s the only change. I look forward to reporting back.