Sorry if I've missed a thread somewhere, I've read several here about fan clutches and am still left wondering something.

1967 Olds 88 Custom, 425/300hp with TH400 and AC. Running a stock-spec 195 degree thermostat, since I'm opting to go with what the Olds engineers originally prescribed.
Fan clutch is legally dead, fan freewheels like crazy when the engine shuts off. Which fan clutch is most appropriate for this setup? Should I be looking for a same-number NOS clutch (which may be pricey) instead of just going with a cheaper "standard" (aggressive) new-manufacture clutch?

I do live in sunny AZ; we see nasty temps for more than half of the year, and I do plan to run AC constantly during summers once I get the AC system in working order, but I don't know that I want a fan clutch that will have my fan roaring year-round, especially seeing as I hope to make this car my highway cruiser once all the kinks are ironed out. Then again, I'm well aware that I might not have any choice in the matter unless I feel like swapping clutches every time the seasons change. Suggestions, ideas?

On that note, my radiator is shot, leaking from the driver's side tank and from somewhere in the cores. I'm planning on buying a new one this weekend. How many rows are in the original rads for this kind of setup? I've been told 3. The rad I'm looking at is a 4-row from Murray, which I imagine can only help with cooling once summer returns, especially if it ends up paired with a more aggressive clutch than the original.

Thanks

 

Page 6K-5 of the service manual says: "Use of thermostats rated above 180 degrees control temperatures are not recommended."
Page 13-1 of the service manual says:"The 52 through 86 series equipped with heavy duty cooling option use a core 2.7" thick with four rows of cooling tubes."
If you're going to operate the vehicle with the A/C running in the summer in AZ you'll probably need all the cooling capacity you can get. Get a fan that moves some air.
I live in S. Louisiana and have struggled with cooling every summer.

 

I agree that you probably had a three-core originally, but in AZ would probably benefit from a four-core.

As far as a fan clutch, I'm partial to the Hayden 2797, myself. Sounds like a Cessna taking off when you first start it, but quiets down after several minutes of driving.

- Eric

 

Thanks for the feedback, guys.

Just checked my own service manual, and well, I'll be damned. Don't know where I'd originally heard of 195 deg. thermostats being used, but I had been under the impression that the 425s were designed to run at about that temp, and assumed that there was some engineering reason.
Think I'll grab a 180 t-stat but just leave the 195 in there over the next few months for winter warm-ups, provided it doesn't cause any problems during actual operation. We just had our first overnight freeze watch last night and again tonight.

I'll see how this 2747 works out, but I'll certainly have a look at the 2797 if the car's running hot come summertime. At the least I figure I could hang onto the 2747 for winter driving if it doesn't pan out in hot weather.

 

The trend toward higher engine operating temperatures appears to be in response to governmental requirements regarding MPG and emissions. Those forces really weren't felt so much during the 60s. When it comes to lubrication, engine durability, and avoiding fuel percolation, cooler seems to be better. Mine is happiest in the moderate climates once the engine gets to 160F degrees.

 

Yeah, I haven't checked the literature, but I believe that the thermostat went from 180° to 195° in '68 or '69.
The design, metallurgy, and tolerances of the engines, though, didn't change at all, so there is no harm in running a 195.

In the end, it comes down to personal preference. I run a 180 in mine because I want to reduce the chance of detonation at 10.25:1 with modern fuel.

- Eric

 

Ah, okay that makes sense. I could definitely see how making the engine run at a higher operating temp would help give cleaner emissions readings. Given that I live in one of the few places that still happens to test '67 and newer cars, I might keep the 195 t-stat up my sleeve in the event that the car does poorly in emissions testing, but for normal use I think I'll go to a cooler one. Thanks for clearing all that up! Much less confused now.

Fortunately(?) for me, my engine appears to be a 9:1 standard-compression 425, so I guess there's less risk of detonation from running a warmer 'stat in the meantime.

 

In that case, I wouldn't even think twice about it, so long as the rest of your cooling system is up to par.

- Eric