I decided to improve the cooling on my '70 Cutlass. I had already upgraded to a four-row radiator, but the aftermarket flex fan just was just barely doing the trick at idle in traffic, especially with the air on. The original clutch fan no longer fit, probably due to engine mount issues (it hit the bottom of the shroud), and was probably shot from sitting around for a number of years.

In fairness, I'm still not convinced of the accuracy of my purchased-used Autometer electric water temp gauge, but it had hit 250+-degrees idling in traffic. At the same time, however, the factory idiot light, which I'm told comes on at 250 degrees, has never lit (it does light during bulb check. Haven't tested the sensor yet.)

At any rate, I was able to pick up a pair of factory electric fans from an '88 or so Buick Regal (FWD) at the local U-Pull-It wrecking yard. Given the heat produced by the little V6 in that tight engine compartment with very little grille area, I figured these guys might do the trick. As it turns out, the pair are almost exactly the same width as the radiator core! The fans cost me very little, since I wandered into the yard during one of their "all you can carry" sales. I had 5 fans, two distributors, four Mazda aluminum wheels (for my RX-7), a seat belt, and a bunch of miscellaneous crap. All for $25. I love these sales.


Mounting the fans was actually fairly easy. I bought a 72" stick of 1"x1"x1/8" aluminum angle from the local Home Despot, and massaged it thoroughly with my Dremel tool, drill, and a hacksaw.

The lower end of the fans mount in rectangular slots cut in the chassis - they just rest in the holes on rubber bushings. I cut a chunk of the aluminum angle about the same width as the radiator core, cut the slots in it with a Dremel, and mounted it to the factory fan shroud lower mounts, after tweaking the mounts to vertical. I used clip nuts (I love those things) on most of the places where things bolt together, to avoid having to wrestle with two wrenches at once on a nut-and-bolt combo (the clip nuts were mostly pirated off the same car that the fans came out of - they use the same idea.)

fan bottom mount

(All pictures can be clicked to enlarge. Use your "Back" button to get back here)

The fans' bolt into the core support at the top in the original application. Since the core support is in front of the radiator on my car, I had to come up with something else. I used another strip of the aluminum angle to bolt the two fans together, then fabricated brackets to attach the angle to the original radiator top plate, through the original fan shroud mounting holes. Again, clip nuts were a boon here.

Fans Fans, again

fans mounted fans in 2 fans in 3

(The piece of hose zip-tied on to the radiator hose was to prevent the fan shroud from rubbing on the hose. My factory plastic holder strap died.)

While I was figuring out and fabricating the mounting, I was also planning the wire routing. The factory setup routes the wires below the fan - this seemed easiest to me, since the connectors are at the bottom of the motor, and the support frames have built in wire routing clips. Needless to say, I rescued the original connectors when I grabbed the fans. The fans' power wires run down their frames, then along the lower aluminum angle mount, zip tied or clipped at strategic points. Everything heads over to the driver's side of the car, where all the power is. They are grounded at the factory chassis ground on the left core support, and the positive wires go to a pair of relays hidden inside the left fender. The relays are fed from the horn relay distribution point, with a 30A in-line fuse (always, always, always fuse power!) The relays are controlled by an adjustable thermostat that I purchased from a street rod parts supplier at a local swap meet.

Thermostat and relays

(In the picture above, the relays haven't been mounted or fully wired yet.)

The thermostat has a method of mounting the sensor that I'd never seen before: instead of snaking the sensor bulb into the radiator hose, or sticking it into the fins of the radiator, this little jewel replaces the drain petcock with a compression nut and sleeve tightened onto the bulb, which is sticking into the radiator tank. No leaks so far. This thermostat also has a normally-closed (closed when cold) contact to use if you want the fans to come on with the AC regardless of temperature, or as a manual override. I used it in the former method. I also connected the thermostat's normally-open (closed when hot) contact to +12V battery, just like a factory setup. This means of course that the fans will continue to run after the car is shut off. Other people may prefer to wire that to ignition, but I have had no problems with it running the battery down. The trick is to set the thermostat to just below the coolest temperature that the fans can maintain. No point in having them come on at 150 degrees if the best that they can maintain is 210. Mine can manage an indicated 200 degrees, so I have them set to around 185-190. They only stay on about 5 minutes after the car is turned off.

All wiring is enclosed in factory-style split-looming, and routed out of the way of anything that could cause trouble.

Just for fun, here's an example of how much air these little guys move:

suck it up!

That shop rag is being held on to the grill solely by moving air! Even with the AC on, at idle, I have yet to see over an indicated 210 degrees, however, the fans do pull a bit of a load. The alternator can only just maintain an indicated (the voltmeter is tapped into the ignition wiring under the dash, so there is a little voltage drop from what's at the battery) 12V with the car idling (normal idle) in gear. A little over 12V idling out of gear. About 13+V just off idle. My alternator (an 90A internally regulated later model GM) normally sits at 14V with the fans (and headlights) off. I haven't had a chance to measure at the battery/alternator yet.

Any questions? Email me!