Electric fan


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Okay, after buying this '73 Riv GS last year--it has been almost a perfect runner/performer.

the last owner put too much money into it ($1500 all stain-less steel dual exhaust system--that looks like a work of art, and sounds even better, a new 134a A/C system, a new vinyl roof, an Alpine stereo-- that was the first thing thrown in a dumpster---a 'new' interior of '89 T-Bird Sport Coupe suede/leather buckets and a small Grants steering wheel.)

So last Autumn, the water pump started to drip. This was a good opportunity to put in a new TA water pump, 12-SI 94-amp Delco alternator,new gates hoses and belts, and the largest flex fans with the thickest metal on the 'flexed' edges, a 180 degree thermostat, ACCEL 71105e billet distributor, OLD-original Jacob's Ultra Coil (with the variable magnetic core, which continuously adjusts spark intensity according to demand). new 16.5 psi cap (you would never thing that these go bad, but the original was leaking). It was running great, even with the MAX A/c on, and never boiled over.

While driving in some heat in the summer, I was in stop and go traffic, and the radiator cracked. It was the original 4-core one.

Instead of getting that one fixed--which i should have done, since it was in excellent shape, with NOT one bent fin, I ordered some Proliance 4 core with the exact same dimensions. I also changed the thermostat up 195.(190 is stock according to my Buick manuals) to get the engine at operating temp as quickly as possible.

Well,this summer, I went to a GM car show--not intending to open the hood--because it is far from detailed, and even the car has poor paint job; but the car has NO rust, no dents, and looks good form 20 feet away.

Wouldn't you know it, after going 80-90 on the highway,and getting off in a 30 minute idle crawl to the state fairgrounds, it started over boiling over--which is one of the most humiliating thing to have happen. People swarmed over to the car,exclaiming, "Your radiator hose is bursting!!!, this part is not painted the right shade, this part is not plated correctly, etc--a bunch of gratuitous unsolicited advice, making this show a humiliating experience.

This is far from a show car,and it was never my intent to turn it into one--just a reliable car, where performed amazingly well on several trips in the long trips in the winter/Spring

So, after "burping" the system,to get all air out by opening the heater core, I filled up the radiator. I was using about 1 50/50 mix or distilled water/coolant. water has a much higher specific heat than ethylene glycol--so many sources said i could get by on 30/70 in the summer (30% distilled water).

After all that, and flushing the engine of new coolant at each time (when i got the car-all fluids were new), it doesn't boil over, but it does seem to run hotter.

Okay here is the "sticky" part: I use that heavy duty flex fan 18" x 6 instead of the 20" x 5 stock thermo-torque fan clutch. Using all the largest spacer, the fan is still about 3.5" away from the radiator. And I know it also has to be as close as possible to the fan shroud). It still pulls in a a lot of air at low rpm, so much so that the air sucked in is very noticeable if I put my hand up to the A/C condenser.

I certainly could go back to the 20"x 5 stock fan with a the clutch. yes, flex-fans do rob the engine of more power than the thermo or torque-disengaged fan clutches--but they have worked for me on my old cars that mainly do cruising duty.

here's my question: Should I get rid of the mechanical fan, and use a Zirgo 3000cfm electric radiator puller fan by itself, or with the flex fan--either where it's at, or spaced 1/2" more away from the radiator?.

or: use two 10"electric fans in front of the A/C condenser???--like my Lexus does ( it was a mechanical one, as puller, and two smaller ones that just go when the A/c is under extreme conditions

Also I think the 180 thermostat seemed to perform better--the engine still warmed up quickly, and was at a temp that the fan clutch also engages.

if I used just the largest electric fan I got, could save maybe 10-15 HP??

Another factor is the A/C, while i was driving to the state fair auto show, speeding and having the A/C on, I noticed the A/C compressor smoking, which could have been a drag on the engine. Obviously that has to be replaced. It must have been a a low-quality rebuilt one to have worn out in less than a year.

Any comments on my questions in bold?


I have an electric fan from a 90's Volvo on my 350 Buick which works fine. I also have electric fans made by derale on my 455 Buick, which again works fine. I'd recommend that route as it opens up the engine more, and it works great. The only thing I don't like is that if the car is already at operating temp and you want to start it, the fan is drawing current and so is the starter. It's an easy fix to disable the fan initially, but I haven't done it yet.

You can get a wiring kit from Painless for about $65 from Summit, or just buy parts individually and wire it yourself. All you need is a relay (for whatever amperage you need, I used 30A ones) some wire (at least 12ga for the main power and ground, 16ga is ok for the signal wire to the relay) and a temp sender that goes into your intake manifold (that you'll probably need to get from Summit.) If you do it yourself, it'll cost about $25 and may end up looking better. If you go that route and want help with it, I can walk you thru it just email me.



Active Member
Thanks so much for the info.

This is one part I like about these Buick forums and clubs--members have a wealth of info.

Wiring is not an issue, as going through college I worked P/T as a high-end car audio installer.

I have a bunch of Bosch 30-amp relays, and could fuse a 10 gauge wire form the battery to the relay, and another #10 to the load, and use a low-current/smaller wire to a toggle switch in/under the dash to ground--this would activate the relay, w/o the need for heavy gauge wire running from a switch to the load.

or I could get a 180 degree thermo-switch, which would turn the fan on at 180 and off at 185.
Really, I prefer the manual set-up. I also ordered some autometer temp/voltage gauges.

There should be no reason why the stock one wasn't isn't sufficient.

What got me confused gas a question posed to different radiator manufacturers--which type of fan do you believe is the most beneficial?

Answers went all over over place--some liked the flex fans for low-speed driving; other felt a the best stock fan with a working fan clutch is sufficient; others suggested adding a pusher in front for the A/C condenser;

One guy did recommend a stock mechanical fan with an electric as a back up or for extra-stress applications: pulling a trailer, lots of low speed driving in hot climates, etc.

and the flex fan just is NOT close enough to the new radiator or the shroud made for a 20" fan.

At this point I just want a reliable fan immediately adjacent to the radiator. Is 3000cfm enough for a '73 455-5?

If I have room, should I keep the flex-fan or use the stock fan that can be moved back to accommodate the electric one? 3.5" is what the manufacturer claims is the electric's fans depth. That may just barely fit in with the flex fan, where that's at now.

I think I might be able to sqeeze some minute extra HP without a mechanical or flex fan. And the Delco 12-SI 94 amp alternator, seems much better as the 63 amp 10-SI stock one: higher voltage, faster starts from a battery being fully charged and that ignition system ( I don't want to get into; it works, and i get better gas mpg) .

I wish I had added an electric fan on a Toronado GT w-34 I had.

Thanks for any help again. it's appreciated.



I would assume 3000cfm would be enough, but I went with the biggest I could get for the 455 car:


It's a 4000cfm puller fan and I have no mechanical fan. I can't really say if 3000 is enough, but you could try calling the tech department at Summit or some other place and ask them. Also the fan I got from a Volvo for the 350 car works really well, although I don't know how much air it flows. When it's on and you put your hand in front of the radiator, you can definately feel a strong pull.

You could get the 3000cfm one and give it a try. If it's not enough, you'll find out soon enough:bana:
Several points on fans.
- Your fan is really only used below 20 MPH. Above that, there is plenty of airflow to do the cooling.
- A tech from Flex-a-lite told me "an electric fan will never pull as much air as a mechanical fan". If a salesman endorses his "competitor" I tend to listen.
- The best mechanical setup is the stock fan w/ clutch, you should get a "tight" clutch (stock ones seem to slip too much according to consensus, maybe try one from a suburban)
- A mechanical fan should be 1/2 in the shroud, 1/2 out. You don't want it sticking too far in or too far away.
- The condensor will reduce overall airflow, it acts as a restriction (not to mention pre-heats the air).
- A radiator with fewer fins/inch will allow more airflow than ones that have more fins/inch, more more fins/inch means more cooling surface area. Radiator designs vary from 9 to 16 fins/inch, most are in the middle.

I have a 455 that runs hot, so I had a custom-made 5-core copper/brass radiator. I used to have aluminum but when it leaked nobody could fix it- any radiator can repair copper/brass with a propane torch and some solder. My radiator is probably overkill, but the engine does stay nice and cool.

I took away my mechanical fans to make more space. I use dual flex-a-lite puller fans, plus a pusher fan- when all 3 fans kick on they really move some air. If you want to go with a pusher/puller combination, you should intentionally misalign them so they all hit different parts of the radiator.

-Bob C.
By the way, if you want to use one of those slim flex-fans, you can use two of them on the water pump shaft- one on each end of a spacer. This will give you a "shroud" effect (and really pull some air).



Active Member

I did use the 2' spacer on the biggest flex-fans. of course i know fans are only an issue when the car is idling or the car is not moving a moderate-high speeds. I could add another 1" spacer to that 18"x 6 blade thing--it's already out because the Zirgo ZFB16S 16" electric was too close to the flex fan (it was touching. the electric had a 3 1/2" width). the stoc fan is a 12' x 5 blade thermo-torque unit. That should meet thecar's requirments.

Although I was also looking at ways to get some extra HP--and the HD flex fan was a drag on the engine

but even the 20" x 5blade stock fan in my '76 riviera-- with a '70 engine-- in another of my Rivieras is not that close to the radiator. It never has overheated.

The 16" 300cfm electric really seems to pull MUCH more heat than the other fans.

I was thinking of adding two pushers in front, like you said for the A/C condenser. My Bosch 20/30 relay was entirely inadequate for this fan. The alternator case would be scortching hot to touch and the Bosch relay for the fan was hot.

i now have a 75 amp relay, and switch in the car, with auto-meter gauges.

here's what I loathe:

The thought of changing the head gasket. In the Buick manual, it says when an overheating incident occurs, to torque down he head gasket. On this car, it is probably the original one. I feel that exhaust air is entering the cooling system:

I'm sorry but this is pissing me off---this overheating when the original radiator burst I believe must have caused damage somewhere. the Buick service manual says head gaskets are easily over-stressed in an overheating situation.

The car was running better than any car I have ever had from when I did my first TA water pump/new 12-Si alternator/ electronic ignition/much more work, etc. It ran SOOOOOO smoothly from Aug '06 to June '07 when the orig 4-core radiator burst.

So, I know, starting with my flex-fan, with a NEW 4-core radiator (proliance), it overheated at a car show, driving fast on the freeway, and then idling a long time.
If I drive short distances (10 miles) at night with my new Zirgo ZFB16S fan--which pulls more heat than the other fans (original clutch-mechanical one and the flex-fan), it is better, but after sustained driving, it over boils over even with a new 16psi cap.

Air must be entering the cooling system--my guess

This engine is still great;no oil burning; spark plugs are extremely clean; idle was great.

It is still a great engine--and I want to kepp it that way.

The '76 ( basically the same engine bay set-up--actually a '70 455 block with stage 1 heads the orig owner had installed from the dealer in 1976, but otherwise 100% stock--except for HEI upgrades--an issue i don't want to get into). It has NEVER overheated-even with my CA Desert driving 0where i bought the car)

****What should be my next step?
****Do have to start the head gasket install?
Really, I need some advice on this


Active Member
By the way, if you want to use one of those slim flex-fans, you can use two of them on the water pump shaft- one on each end of a spacer. This will give you a "shroud" effect (and really pull some air).

That's a good idea, Bob. But one reason I wanted to take the flex fan off was the added stress it placed on the waterpump bearings.

the electric fans seem the way to go because the puller fan is mounted directly to the engine side of the radiator--no distance issues; less HP loss from the engine. And physicall feels it pulling a LOT of heat and air.

The engine has been flushed about 5x in the past year.When I bought it, a GM dealer redid the whole A/c system and flushed the system. after all my worked on it, the engine was flushed.

But in this lexus LDS 400 I have, it has a mechanical temp or torque fan as a puller and two big, electric pushers in from of the A/C condenser, when they are needed. it NEVER goes over the midpoint for temp operating conditions.

What should i do with the '73? I love this car, and do NOT want to destroy this engine.


Active Member
today I got a 75amp 12V relay. I found my 16" Zirgo fan, rated @3000cfm, was drawing about 25 amps( not the 12-20 they claimed)--and a 20/30 Bosch relay was causing a LOT of resistance: the relay was hot, and the 12-SI 94-amp alternator was burning o the touch. I may add more lectric pusher fans in front; hence the 75 amp relay.

so I have the new 4 core radiator. I'd like to go with one of those new aluminum 2 row 1" tube radiators. .

Many radiators have specific requirements for their radiators--some life a flex-fan (because there won't be problems with the clutch, and it pulls at low rpm), some think a stock fan is fine, other gravitate to the electric by itself or in combo with a stock fan.

MY electric fan is wired with 10gauge wire to the relay (about 5 feet, and three feet to ground). I have a switch inside that turn the fan full-on or off, by grounding the relay.

---But tell me: if I have this set-up with this electric-fan REALLY pulling much more air than either mechanical fans, what is required for a street 455?

----Do you think I have air entering the cooling system? (that's what the Buick Service manual states is a probability after overheating).


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I got my original 4-core radiator fixed (they said it was better than the "new" one I bought), and am going back to the original.

I think as bobc455 says, going with the stock mechanical (1/2" from shroud and 1/2 in the shroud, may allow me to use the Zirgo ZFB16S, too.

Or I could go back to the flex-fan from Summit--with thicker pitched fins. The electric puller will not fir with the 2"spacer.

No one can give me an answer (even TA)about the cooling demands of a mostly stock'73 Riv GS.

One thing I've noticed is my new 12-SI 94-amp alternator case is burning hot after a drive. I have my fan wired either to be completely on or off. I'm looking for a thermostatic control. Even my new 75 amp relay is warm to to the touch. Zirgo said that fan may use 25 amps continuously. my wiring is sufficient. 4 gauge from alt "+"post to the battery. 1o gauge fused at 30 amps to a tyco 75 amp relay, 5' of 10 gauge ground and power wires, 16 gauge switch to ground that activates the relay.

IF I add electric pushers--only 2 10" may fit because there's a structural element that divides the condenser.

And my alternator isn't going to take much more of this. I'm planning for a sstealth audiphile stereo with 60-amp rated high-current amp. Rarely does it take that much, but they do have needs for instantaneous high-current capability. My new ignition system is fused at 15 amps (it still works great, but the old-style jacob's Ultra coil seems to get somewhat hot on the heatsinks )

I'm going up to an alternator with more current at lower rpms.

any more suggestions for the cooling part?

I'd love one of those 1" 2 rows, which are better at dissipating heat, but if I can return the new proliance one, and put in the original 4-core one(that was tested up to 20psi), maybe use the stoc fan/clutch--which worked when I put it a sink of hot water. (I still wishe there some that locked up more quickly.


Active Member
I would assume 3000cfm would be enough, but I went with the biggest I could get for the 455 car:


It's a 4000cfm puller fan and I have no mechanical fan. I can't really say if 3000 is enough, but you could try calling the tech department at Summit or some other place and ask them. Also the fan I got from a Volvo for the 350 car works really well, although I don't know how much air it flows. When it's on and you put your hand in front of the radiator, you can definitely feel a strong pull.

You could get the 3000cfm one and give it a try. If it's not enough, you'll find out soon enough:bana:
That summit dualfan looks almost perfect. Doesn't it fit the stock '73 cross flow core??

Do those nylon fastener place stress on the radiator?

After using just this one, what was the operating temp of your Buick 455?


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I'm going to work on this project tonight. But I feel that bobc455 has gave a great example of what would fit in the core section.

50 amps continuous is a LOT of current!!! Idling --when the alternator puts out its least current, is going to be taxing it.

On all my 455's I used a Delco 94-amp 12-SI (called old reliable for its almost problem free long-life.)

I ordered a 140 amp alternator that kicks out 85 amps at about 800rpm and the full 140 amps at 1200rpms. It sounds to good to be true.

When i had gone through many on my '63 Riviera, I was always sacrificing low rpm output vs high-rpm/current output.

Even the last handmade 12-SI built by this good small father-son business.The only problem with theirs is that current doesn't start kicking in at low rpms, as indicated by the flickering GEN light on my dash.

Yet i bought a re-manufactured, lifetime warranty on a ebay 12-SI that definitely keeps voltage stable even when crawling with A/c on.

That on 3000cfm fan takes 25 amps. Adding up all the other electrical loads, one finds that even that 94 amp alternator is not equipped to meet my needs.

My '76 Riv (with a very unusual '70 stage 1 block and heads and no smog control (besides a PCV valve) seems fine with it 63 amp 10-SI

But my '63 is going to have a simple stereo system with 2 speakers and one Tube Driver 4 x 50 amps amp that can draw up to 60 amps (rarely).

I think I'll put the original, cleaned, welded, stock radiator back in, install the electric puller and use the stock thermo/torque clutch 20" x 5 thermo fan.

On e question: If its new electronic dist and coil have this 0.065" to arc will that cause any over heating? It never did, after I was finished with that install last autumn. Of course winter driving is not an indicator of real world summer temperatures.


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Last night--all night--I replaced the new radiator with the old one that was repaired, and added the Zirgo 16ZBFs 3000cfm electric fan. While having the engine running for 15-20 minutes, and driving to my my parking spot (about 1/2 mile away), it still boils over.

During the addition of coolant, it seemed to be circulating, and new thermostat did open.

The fan was in the original shroud (the fan just fit).

I feel, after the first over heating, there's some air leak into the cooling system.

the fan was pulling A LOT of air--and cooling off the radiator very well.

Now, according to the Buick service manual, after a major overheating, the head gasket should either be tightened or replaced. I don't think it ever has on this car.

I have replaced every other piece on the cooling system.

new TA water pump

new thermostat

new fans (biggest flex-fan)

all new belts and hoses.

3 radiators (a supposed replacement, a 4-core replacement--which is the stock size) and the welded original--which was in better condition than the new ones.

I do not want to ruin this engine, as it runs extremely well (and ran cool from last late summer to this June, after replacing the water pump and adding a flex fan last year).

Now what should I do???

Check out GRIFFIN RADIATORS Aluminum 2 row 1 1/4 inch core.....use a DERALE fanshroud with dual PULLER fans (4000 cfm)...do not use Derale's fan control. Here is a pic of the set up I have in my 67 GTO ( almost 800 HP with blower, AC, PS).....I have a 71 Riv...and will install the same system when I "do' the engine compartment. There is no reason a good radiator and stock clutch fan shouldn't cool your car.....as it did for many years....you may have other problems...(bad thermostat)......The set-up I have works VERY well. Eric PS. Flex fans would be my last choice. IMHO.


This again…My van stays cool, no problems now or ever. BUT, somewhere along the way the van has become oh, so loud. It screams running down the road. I asked the tranny shop, after their r&r if it could be the trans and they said no. I took it back to the AC shop and asked them, they said it could be the fan clutch. They swapped it, but no change at all. I checked it myself, spins free when cool. Well, it doesnt actually spin, more like it moves, with friction. Im told thats okay.Now, once again, Im considering swapping to an electric. I picked up a brand new Flex Fan Black Magic set up for next to nothing. Prior to my swap, I think I might disconnect the fan and drive it for a short run, if quiet, Ill know for sure its the fan set up. Hmmm, I wonder if they put the fan on backward, possible? Anyways, you can go to www.epicvin.com and enter the VIN# to find out whether it was really spoiled or not and if it has undercarriage damage or accessory bag/box glass cracked. Costs cheaper than carfax though and it also has pictures of all vehicles.