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Clutch fan conversion on a 55


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Previous attempt at replacing stock fan:  http://forums.aaca.org/topic/190214-not-all-of-my-schemes/#comment-957447

This scheme did not turn out any better.  6-blade, same diameter as stock, same orientation in shroud.  It moves air, but not enough.  The car runs 10* hotter than expected at all speeds.  Maybe the part is defective out of the box; maybe I need a heavy duty version (that I have never had to use on any other car with a clutch fan).  So it is back to the noisy old stock type fan:  turn the radio up!

(Part No 215011 and  Part No 220618 at Advance Auto)

Willie

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I've considered all fan options in the past: flex, steel, clutch and electric and I've come to the conclusion that anything attached to the water pump is just going to put a bigger burden on the engine than the stock fan. The more blades,  the harder it has to work to chop the air, and you can't run the stock blade with an electric fan because of the turbulence the two fans create.  And then I ran into the same problem as you - there isn't an electric fan big enough to not off set the charge capacity of the system. Even when running an electric choke before going back to the heat stove put a slight drain on the charging system. 

 

When I was getting ready for my dual carb setup, I was originally going to run an alternator with an electric fan plugged into the vacant temp slot on the head and electric chokes. The cut out concept is the same as the generator, the relay is grounded out through the field terminal - either on the Mopar or GM alternator plugs  (Ford I'm un familiar). All that was required was a cheap diode so charge couldn't back feed to the alternator. I ended up swapping back in the generator because I didn't like the way you have to shim the alternator in to fit the stock bracket that is unfortunately a motor mount. 

 

In the end, might just bite the bullet and buy that $400 power master alternator and not have to worry about it. I've heard you can put alternator guts in a generator case, but I've never seen it done. 

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Just for fun, heat and twist each blade to a more aggressive angle so it will move more air.

 

I would try the heavy duty clutch. I believe it require less heat to engage. The heavy duty clutch was my last resort on the ever overheating 455 in my Estate Wagon.

 

Perhaps replace the 180 stat to a 160 to compensate for the less efficient clutch set up.

Edited by avgwarhawk (see edit history)
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I did some research on the supplied part numbers.  One place said the clutch would start working at 170 degrees.  I also tried to cross-ref it into other applications and found that it fits MANY Fords of the late '60s and early '70s, plus '61-'64 Chryslers (which needed a very short shaft for clearance).  I'm not near my ACDelco book with the size specs, but figured I could find something similar online

 

By the middle 1960s, most clutch fan fans were 7 blade and aluminum.  GM also had a factory flex fan on some applications.  My '77 Camaro 305 w/ac came with one, but 350s came with fan clutches.  In later times, I replaced it with a later factory fan and fan clutch.  That's what is still on it and has worked better tan the flex fan seemed to, as it aged.

 

ONE key to effective fan clutch operation . . . is that the thermostat on the front of the clutch SEEs heat in that area of the air flow through the radiator.  For example, in a cross-flow radiator, if it has become clogged, the actual heat dissipation can mostly occur ABOVE the centerline of the fan clutch.  The air through the radiator feels hot, but the temp gauge looks like it's not cooling well.  Doesn't matter if the cross-flow radiator is slightly clogged OR just low on coolant, if the main heat dissipation takes place "not in the middle of the radiator core", the thermostat on the clutch doesn't acknowledge it.  This might not apply in the same manner in a non-cross-flow radiator, though.  A check with a non-contact infrared "heat gun" can help diagnose this.

 

The fan diameter on the Camaro looks "small", but it flows air.  The aluminum fans on our '66-'72 Chryslers are 7 blade and flow air, but are larger than what's on the Camaro.  Seems that by the middle 1960s, fan designs had reached a plateau of efficiency, sound control, and durability.  Not unlike the factory a/c systems of those times.  Fan shrouds evolved from metal to plastic in the same period.

 

There were also some other vehicular features/updates which also seemed to increase cooling performance.  Some makes tended to be more intense in these things than others did, by observation.

 

As y'all might suspect, there are MULTITUDES of fan clutches for Chevys.  That one clutch part number Old-Tank references, in one catalog, showed to fit a '55-'57 Chevy V-8, with many applications being ('68 Buick Special 250 6-cylinder) for newer vehicles.  My original search for a better-than-stock fan clutch for the Camaro was the '79 Chevy Nova 9C1 police car, which turned out to be a Chevy C-30 pickup application, as I recall.  As long as the pilot hole and center shaft length (dimension from the water pump mounting flange to the fan bolt pad surface) works, the final application it was originally used on isn't all that important.  Fan bolt diameters are pretty standard, too, but that spec can change.  Prices, physical amount of aluminum (and related "fins"), and if it has a slotted mounting flange or a drilled mounting flange can vary.  So "substantial" presence can be a selling point for one particular clutch over another clutch of similar dimensions and application.

 

One thing might be . . . to get one of the aftermarket radiator companies to build an aluminum core (HIGH efficiency core and fin spacing) radiator with composite tanks (in the correct cosmetic orientation for OEM stock appearance), shaped and configured for many older vehicles.  Then supply a plastic fan shroud (even a two-piece shroud similar to what GM used in the 1970s) for enhanced cooling.  That would be ONE killer radiator, but would look pretty much stock.  I've got what ACDelco termed "upgrade" radiator in my '77 Camaro.  I think the OEM application is for a mid-80s ElCamino (which is composite).  It has a 1" larger trans cooler in it, so I had to hand-reshape the lines a little, but it took about 45 minutes of idling in the driveway to get the 180 degree thermostat to open after I installed it one late-spring day.  Holds a little less fluid, than the 3-cord Modine it replaced, too.  Just a thought . . .  Of course, you could get one "all aluminum, welded tanks, and such" but it wouldn't look "close to factory".

 

NTX5467

Edited by NTX5467 (see edit history)
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What I don't understand is that even at highway speeds (55-65mph) it cools worse than the mechanical fan.  Fast idle in the driveway and checking temps shows that it seems to start engaging at 200* and and is well engaged at 220*.  It may never overheat, but I don't want it running that hot.  I am happy with my 180* thermostat regulating.  On hot days it does get to 220*, but that is because it is HOT outside.

Maybe it is defective or calibrated for contemporary cars with 195* thermostats even though it is used in 66 chevy, 66 skylarks, 80's f-350s..

Nothing wrong with the radiator if it cools well with a the mechanical fan.

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Perhaps the base aerodynamics of the vehicle are such that too much air is going around the radiator that through it?  Hence, the need for the fan to pull air at highway speeds.  Many modern vehicles usually have some sort of "air dam" behind the front bumper of under the radiator, to deflect air to the side and create a low pressure area behind the radiator, resulting in more air naturally coming in through the radiator (either some metallic design feature or a plastic deflector), but then '55 Chevies were probably similar to the Buicks, aerodynamics of the front sheet metal/bumper-wise.  Compared to some other brands, or later designs, it seemed that GM just put the radiator "in an air flow" and expected it to cool well.  No real "help" to ensure that a majority of the "radiator air" would go THROUGH the radiator rather than around it.  (More thought required)

 

NTX5467

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Could it be that the clutch fan is actually impeding air flow through the radiator?  Similar to what NTX5467 suggests, but maybe the additional blades (depending upon how close the fan is to the core) actually spoils the airflow when the clutch is not engaged?  Does the car have a fan shroud on it now?

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When I had the GM flex fan on my Camaro, as it aged, it acquired a "creeping heat" issue. The longer I drove it, the more the temp needle would creep higher, but never past 210 on a 180 thermostat.  I replaced the radiator with a Modine 3-row and that helped, but not all of the way.  I suspected that as the flex fan blades "feathered" at higher road speeds, that it could be blocking the air flow through the radiator a little, so I got a new OEM GM replacement.  No significant change, although the spring action in the blades seemed a little "newer".  Until I put the fan clutch and Camaro fan clutch fan on it, it persisted.  Never to a really high temperature, but higher than what it should have been (similar to what Old-Tank's vehicle is doing). 

 

NT5467

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13 hours ago, EmTee said:

Could it be that the clutch fan is actually impeding air flow through the radiator?

I am thinking the same thing:  put a 7" disc (fan clutch) in the flow along with slow turning blades in the flow through the radiator and it is worse than having no fan at all!

It is out of the car, the 6 blade mechanical is re-installed and working fine.  A clutch fan will never work on a 55.

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The other thing to consider is that (as far as I recall) clutch-type fans are always used in conjunction with a fan shroud (full 360-degrees).  So, if the clutch is freewheeling and the car is cruising down the highway the air through the radiator is forced to spin the fan.  Without a shroud, the fan and clutch are an obstruction, forcing air to bleed out the edges of the radiator (or around it).  That's purely speculation, however...

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The non-thermal clutch fans are purely rpm-dependent on being engaged or not.  Engaged at lower rpms, disengaged at higher speeds.

 

If you're going to consider the fan clutch hub as an aerodynamic obstruction, what about the water pump pulley?

 

NTX5467

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7 hours ago, NTX5467 said:

If you're going to consider the fan clutch hub as an aerodynamic obstruction, what about the water pump pulley?

 

Well, at least the pulley is set back a few more inches and has a conical profile (smaller cross-section closer to the core).  Like I said, I'm just guessing what may be happening based on the observation by others that the steady-state cruising engine temp went up after installing the clutch fan.  That pretty clearly points to reduced radiator capacity.  Assuming that the only change was to the fan assembly (i.e., the radiator was unchanged) I'm speculating that it must be the result of reduced airflow through the radiator core.

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I know Willie's car runs fine and he is just trying to improve it a bit. He likes monkeying with setups. After they fail, he usually offers the old parts to me at a 2% discount. :) 

FWIW, My wagon was recored with a larger capacity core and I run a five blade flex fan, which cools it fine. I had to trim the edges off of the fan to fit within the shroud which means I have five razor blades waiting to bite me in the engine compartment. 

Just for fun. What would happen if you took the fan shroud off? Would that take the clutch size and proximity to the radiator out of the equation? Still allowing air to pass? Like I said, just curious for more engineering type feedback. I'm not changing my cars even though I'm sure I will get a real bargain on a slightly used fan / clutch soon...

 

 

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IMG_0220.JPGIMG_0221.JPGIMG_0222.JPGIMG_0223.JPG

 

A few pictures to show what I am dealing with:  the assembled clutch-fan assembly and radiator shroud with the attached electric fan from my previous attempt.  The electric fan had no effect on cooling at highway speeds whether is was on or off, but was less efficient when in congested traffic than a mechanical fan.  Advertised at 2100 cfm and 9 amp it could not keep up and the real amp draw was 12 amp and that was maxing out the 30 amp system with the a/c on.  There are 3500 cfm fans out there that would probably work, but that would require more money for that fan and an alternator...that's where I quit on that scheme.

Now if Mikey wants to invest in a 3500 cfm fan so he can eliminate cuts on his tender hide, the setup is ready to go :lol:; or remove the shroud and try the clutch fan.

Willie

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I'm very surprised the 6 blade with clutch does not keep the engine cool.  This fan/clutch set up has been the bread and butter for years.  I can't fathom how the dinky standard solid fan keeps the car cooler.  It logically does not make sense.    

 

Do you physically hear the fan engage when hot?   At highway speeds, as we know, it is to disengage and free wheel.   Are we saying that the standard fan set up is pulling air like mad at highway speeds thus keeping the engine cool?  If we are, logically then a heavy duty clutch that stays engaged at higher RPM would act like the standard fan.  Thoughts?    

 

As a side note, my heat creeps ups at highway speeds.  I believe air does find it's way around the radiator at highway speeds.    

 

Edited by avgwarhawk (see edit history)
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20160807_135548.jpg.52d720ee1d3ad222e9d4de7b87989cf9.jpg

This is the stock 5 blade fan for a/c cars.  I am using a similar 6 blade from a parts car that had a sears allstate unit that seems to cool better.

The fact that the car with a non running electric fan cools better at highway speed tell me that the fan/clutch setup is somehow blocking flow with the combination of parts on a 55.

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The surface area the stock blade set up has compared to the 6 blade replacement can't be much more.   I suspect the stock blade is pulling like crazy at speed.  The clutched fan is free wheeling at speed and allowing air to make it's way around the radiator and blocking some to boot.  I would think the heavy duty clutch would solve the problem.  However, that is a darn costly experiment. 

Edited by avgwarhawk (see edit history)
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I would look toward a more heavy duty clutch that is spinning that fan close to the shaft speed.   Similar to the standard fan set up.  

 

Standard Duty Thermal 
Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch. (1-1/2" of pitch) Flat plate impeller design with 30 Sq. In. of working surface. 
Heavy-Duty Thermal 
Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans. (2 1/2" of pitch). Land and groove design with 47 Sq. In. of working area allows higher operating RPM's. 
Severe Duty Thermal 
Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 Sq. In. of working area. Larger working surface provides cooler running and longer life expectancy.

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Fan Clutches
Standard vs. Heavy vs. Severe Duty
One of the most common questions on fan clutches is, “What is the difference
between a Standard Duty, a Heavy Duty, and a Severe Duty fan clutch?” The following
TSB will attempt to shed some light on this issue.
First, we must understand the operation of a fan clutch. Normal operation of a fan
clutch is to be engaged on start up. After a few minutes it should disengage and quiet
down. When the air coming across the radiator reaches a set temperature, a thermal
spring inside the assembly will turn, causing the clutch to re-engage.
When installing a fan clutch make certain that the clutch you are using is designed
for your application. Fan blades with a pitch of under 2 ½”, require a Standard Duty fan
clutch. Blades with a pitch of over 2 ½” can use either Heavy Duty or Severe Duty
Clutches.
Standard Duty fan clutches are usually installed on cars and light trucks designed
with good air flow. Due to minimal airflow requirements, the fan blade equipped on
these vehicles, have a relatively low blade Pitch. The Pitch on a fan blade can be
measured by laying the fan blade on a flat work surface. Measure from the work surface,
to the highest portion of the fan blade. The pitch on Standard Duty fans is typically under
2 ½”. Since these blades are under 2 ½”, the fan clutch is designed to disengage with
minimal resistance. These fan clutches are designed to turn the fan at 60 – 70% the speed
of the shaft it is attached to.
Heavy Duty Fan Clutches are applied on vehicles with a higher demand for
airflow. As you would expect, increasing the pitch on the fan blade will increase airflow.
If the pitch of the fan blade is increased, the resistance on the fan clutch will also need to
be increased. A fan blade with a pitch of 2 ½” or over, will require the use of either a
Heavy Duty or a Severe Duty fan clutch. If the wrong fan clutch is installed, the fan may
spin freely and fail to produce adequate airflow to cool the engine. Heavy Duty fan
clutches turn the fan at 70 – 90% shaft speed.
Severe Duty Fan Clutches have the same operation as Heavy Duty fan clutches.
The difference between them is in the “Working Area”. As a fan clutch spins, it creates
heat, the larger the working area the easier the heat is dissipated. Severe Duty fan
clutches typically have 65 sq. in. of working area, Heavy Duty clutches have 47 sq. in. of
working area. Due to the larger working area, the Severe Duty fan clutch runs cooler and longer life expectancy. 

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As well mounted as that electric fan is, its a fail

It will draw its air from around the edge rather than through the radiator

It is also possible to reverse the fan by reversing the wiring and flipping the blades over

But, if you were going to run an electric fan, I would recommend an alternator, as said, their current draw can get up there a bit

 

 

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1 hour ago, avgwarhawk said:

So what is the pitch of the 6 blade you have?  Is it 2 1/2 inches that would work best with a heavy duty clutch?     

On the clutch fan it is 2 to 2.25 inches...about the same as the 5 blade and 6 blade ones.

1 hour ago, Ttotired said:

As well mounted as that electric fan is, its a fail

It will draw its air from around the edge rather than through the radiator

It is also possible to reverse the fan by reversing the wiring and flipping the blades over

But, if you were going to run an electric fan, I would recommend an alternator, as said, their current draw can get up there a bit

 

 

It did work better than right against the radiator and will pull rags against the grill even with the hood open.  The blades and polarity are set for its position.  Not a big deal to close up the edges if the 3500 cfm did not work well.

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Respectfully curious of the source of the TSB and the specification of "areas" and fan load/pitch on the clutch.  I'd just never seen that information before.  It does make sense there would be some definitions, but I also figured some of that was marketing dialogue to get people to buy the items they really should have been buying in the first place.

 

In the earlier thermostatic-controlled fan clutches, the outer end of the spring was just "in the slot" of the holding fixture on the front of the fan clutch.  Later, they started to put a dab of "epoxy" to keep it in place. Otherwise, you could add a little bit of preload to the spring and get earlier fan clutch engagement, or later dis-engagement (rpm/speed related).

 

In general, though, I'd look for any fan from a factory a/c car from the middle 1960s until the middle 1970s or so . . . or pickup trucks.  During that time, factory a/c reached it's highest plateau of performance, which also meant the air flow through the radiator and condenser had to be optimized too.  Absent of the TSB nomenclature, look for the beefiest-body clutch, BUT it might also be one of the most expensive ones, too, especially if you get it OEM.  But to me, if it looks like what Old-Tank pictured, earlier, I'd say that one or one like it should do pretty well.

 

From my own experience, the BEST fan set-up, performance-wise, is the stainless steel Flex-a-Lite fan.  I put one on the '66 Chrysler I was driving in 1975.  After a 90 minute freeway run in 100 degree Texas summer weather, as soon as I stopped, I could raise the hood and remove the air cleaner without needing gloves as it was "cooler than ambient" under the hood.  BUT . . . even with the 2.76 rear axle, past about 55mph, it sounded like an airplane ready for take-off.  It worked, but noisey.  Had to be careful when the engine was running lest the blades become "surgical stainless steel".  I put the fan clutch back on it . . . it wasn't so bad, after all, after I put two dimples in the fluid reservoir.

 

NTX5467

Edited by NTX5467 (see edit history)
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Ultimately the clutch and fan need to work moving air on the same level as the stock set up but have the ability to disengage when cool enough making quiet operation. The way I see it the standard clutch set up is only rotating half of what the stock fan is doing. From the articles I posted only the heavy duty will get the rotations of the fan close to what the stock fan is spinning.

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At this point I'm just trying to understand whether a fan clutch even makes sense for this application.  If I'm hearing that the fan is needed for low-speed and stop-and-go driving as well as at highway speeds, then when is it OK for the clutch to disengage...?  It seems that a hard-mounted 5 or 7 blade fan (like the stock 5-blade unit pictured above) is the way to go.  For a clutch fan to be useful, it's as if the radiator capacity would need to be increased first, so that just the air pushed through by the car's motion removes the necessary heat.  The thermal clutch would then engage under high-load conditions such as pulling up a long grade or towing a trailer.

 

Now, I was contemplating swapping the hard-mounted 4-blade fan on my '64 GP for a fan/clutch & shroud from an A/C car because it runs a little hotter than I like on a 90-degree day in stop & go traffic.  Hearing this discussion, however, I'm wondering whether that's such a good idea.  Maybe just a shroud with hard-mounted 5 or 7 blade fan would be better...

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13 hours ago, EmTee said:

At this point I'm just trying to understand whether a fan clutch even makes sense for this application.  If I'm hearing that the fan is needed for low-speed and stop-and-go driving as well as at highway speeds, then when is it OK for the clutch to disengage...?  It seems that a hard-mounted 5 or 7 blade fan (like the stock 5-blade unit pictured above) is the way to go.  For a clutch fan to be useful, it's as if the radiator capacity would need to be increased first, so that just the air pushed through by the car's motion removes the necessary heat.  The thermal clutch would then engage under high-load conditions such as pulling up a long grade or towing a trailer.

 

Now, I was contemplating swapping the hard-mounted 4-blade fan on my '64 GP for a fan/clutch & shroud from an A/C car because it runs a little hotter than I like on a 90-degree day in stop & go traffic.  Hearing this discussion, however, I'm wondering whether that's such a good idea.  Maybe just a shroud with hard-mounted 5 or 7 blade fan would be better...

 

Willie is looking for quieter fan operation. 

Edited by avgwarhawk (see edit history)
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When working on cooling system issues, you should do it in hot weather to get a real idea of how it is gonna work.  The problem is you have to work in hot weather --- I have had all the fun I can stand!

Willie

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I think the issue here, as someone had stated before, is the orientation of the radiator in regards to air flow through the front grill. I'm not sure when it happened, as I'm not that well versed in the multiple years of cars, but at some point radiators went from vertical to horizontal mount and filled more surface area of the grill. Open the hood and look through the grill to see how much of the radiator is exposed on our 50s Buicks and it only appears to expose half the radiator. Open a late model with a horizontal radiator and it follows the length of the grill, opening more area up. Clutch fans, as I understand it, work with the air flow through the grill to push the heat off the radiator into the thermostatic controller and thus engage the fan. Maybe your clutch fan isn't working so well because of where the air through the grill is passing through the radiator and thus isn't hitting the controller? The mechanical fan works great because it just pulls air from in front of the radiator, where the clutch fan needs air pushed through the radiator to work properly. The fan shroud is there to guide hot air out, not guide cool air in. Maybe fab up some type of shroud from the front of the grill to the edges of the radiator to maximize where the flow of air is going? Maybe some industrial plastic roofing sheets fastened  from the mounting screws of the grill to the radiator corners? That way you reduce the huge pressure deadzone in front of the radiator.

 

Likewise, most modern cars I've dealt with have two electric fans attached to the radiator (usually turning on at different temps) that span the entire radiator. You electric fan is smaller than the fan shroud, so your efficiency is lacking because it doesn't cover the full length of the radiator. I'm not sure how you have the fan setup on your Ford, but it's engine compartment looks to be much less restrictive. Needless to say, electric fans will most likely be a bust without an alternator.

 

I just wanted to add this last bit in. When I had my radiator rebuilt, I had it re-cored with a third core instead of the stock two core. I also blocked off the transmission cooler on the bottom of the radiator and mounted a separate transmission cooler in front of the radiator (not on the radiator). If 55 is the same, then take into consideration the heat from the transmission cooler heats up the bottom of the radiator. I'm not sure what the difference in engine and transmission temps are, but re-routing the transmission lines to a remote mounted cooler may alleviate your cooling issues.

Edited by Beemon (see edit history)
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There were PLENTY of vertical-flow radiators with clutch fans before the cross-flow radiator came into use circa 1967 on some GM vehicles.  Most had full shrouds, but others just had a "venturi" shroud around the circumference of the fan blade's "real estate".

 

I was at a local cruise-in and the subject of electric cooling fans and older vehicles came up.  In the case of the later Gen IV GM engines, it seems they are now using pluse-width modulation to run the cooling fan(s).  The controlled can be "mapped" for the degree of full speed vs engine temp vs vehicle speed.  Pretty neat for those applications.  It was also mentioned that finding a late-model electric fan array from a cross-flow radiator that was the correct width to vertically fit a (in this case) '57 Chevy radiator would really be NICE.

 

The whole idea of the full fan shroud is to pull air through most of the radiator rather than just the area in front of the fan. I suspect that most of the air flow will be in the general vicinity of the fan.

 

NTX5467

 

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As I said earlier, since the purpose of the fan clutch is to disengage the fan under certain conditions, it follows that in those circumstances there must be sufficient airflow through the radiator without it.  In Willie's case, it seems that at highway speed there still isn't sufficient airflow with the fan disengaged because he noted a rise in engine temperature vs. the same conditions with the hard-mounted fan.  So, the choices appear to be: (1) increase air flow through the radiator (if possible) along the lines of what Beemon suggests or (2) increase the radiator capacity so that the current amount of air can carry more BTUs.  I don't know the condition of the radiator in Willie's car, but certainly 60 years of scale build-up will conspire to effectively reduce the capacity of the radiator relative to when it was new.  If the radiator is clean, then another option is a 3 row re-core as Beemon had done, or possibly replace with a larger capacity stock radiator of a similar vintage (e.g., Cadillac?).  Radiator swaps like that will likely cause a domino of collateral modifications though, so the re-core option is much more likely to give the desired result.  As mentioned previously, putting the transmission on its own cooler (rather than using the one in the lower radiator tank) also effectively increases radiator capacity by eliminating that load.  But -- the trans cooler needs to be mounted where it receives adequate air flow, which is likely somewhere directly behind the grille in front of the radiator.  In that location, some of that transmission heat still gets to the engine radiator via the exhaust air from the trans cooler.  To fully divorce the two circuits requires mounting the trans cooler somewhere else (e.g., under the car) where the exhausted air doesn't then go through the engine radiator.

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Fellas, do the math. The light duty clutch is only producing half the work of the standard solid mounted fan. This is shown in two copy and pasted posts in this thread. Pitch of the blades plays a significant roll as well. I truly believe a heavy duty clutch that will spin as close to the speed of the pulley will work. The other side of it is installing a pulley that circumference spins the fan faster than the standard pulley thus making the light duty clutch more efficient.

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Engine fans should not be required at highway speeds, so if a car gets hot at highway speeds, something is wrong.

decreasing the fan drive pulley increases the fan speed, but also increases the water pump speed and could cause cavitation at higher rpms

I would be looking at the stuff Emtee has mentioned as well as the condition of the water pump impeller, but even something like fuel mixture will effect engine tempreture

 

 

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Kinda working on the same thing in parallel.  Am planning to put AC on my 55 in the near future and wanting to get my cooling system a little more robust, so making sure the "base car design" has enough margin to handle the extra cooling load of the AC for cross country trips - which it currently does not.  In Allentown, stuck in traffic at idle in drive immediately after getting off the highway, the needle pegged at hot which is pretty near 230 on my gauge and the 4 blade stock fan failed to cool it back down to under 205-210 when in neutral and revving the engine.  (Not to mention a charging problem started intermittently at hot, which I can post in a different thread on my findings on mechanical voltage regulators operation after a REALLY hot heat soak.)

 

Not until the car got back under way over 30mph for a few miles did it start dropping back closer to 195.  Certainly the engine might still be tight and have some internal friction, but the cool down rate was not to my liking and just won't do when more heat load from a condenser is added.  On the highway it ran 180-195 ish (an infrared thermometer has helped me to eyeball calibrate the temp gauge). 

 

Upon return to NY from Allentown, installing a 6 blade hayden clutch fan and standard duty clutch (60-70% shaft speed as stated) worked to cool the car down in the local 100 deg weather, and after a heat soak similar to Allentown scenario, but will be unsat for cross country stuck in 100+ degree summer traffic with the AC on.  Not wanting a full time heavy pitch fan,nor wanting to invest in a heftier aftermarket radiator, although either would do the job, am now looking at a 4 Seasons part number 36956 heavy duty clutch (which will turn at an advertised 80-90% shaft speed) and has the required approximate 1.75 inch fan mount height to center it in the shroud) and will experiment with that. 

 

http://ecatalog.smpcorp.com/fs/#/vehicles/parts/num/36956?type=s

 

The sites measurements allow for finding the right size clutch to fit an application and ensure the clutch will bolt up and center the fan in the shroud.  The stock fan is 18 inches in diameter and am going to try a 6 or 7 blade 19 inch fan as the shroud is 20 inches in diameter and giving about 1/2 inch clearance (which is pretty tight) should make pulling air through the shroud more efficient, as well as sealing any gaps with some windshield washer rubber tubing slit down the center to fill the gap between the shroud and frame, forcing all air to come through the radiator.  The radiator is stock size, recently recored and clean inside, don't have any good leads on a 3-4 row and rather like the original Harrison tank and look.  Also going to install a recently rebuilt water pump from Flying Dutchman with the impeller set closer to the timing chain cover and a high flow 180 thermostat. 

 

Am kind of experimenting to maximize how much heat can be pulled from the radiator with the constraints of the original radiator and transmission design. Lots of good ideas on thread and things to try.  Seems the cooling on the 55s was barely adequate to begin with.  Will keep posted on findings.

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Personally, I think I'd start with the 18" fan and more fan-to-shroud clearance.  ONE reason is engine movement under acceleration. 

 

As a lot of the air the fan "spins" ends up at the blades' end, being too tight might put an "air load" against the fan and make it harder for the fan to spin fast enough . . . just a suspicion.

 

One of the main differences in many OEM calibrations is the "cut-in" temperature of the fan clutch.  The engineers might spec a particular temp for a particular vehicle, when new, but after the vehicle ages, they can combine applications as the aftermarket might do initially.  Or on the OEM side of things, if the original production items had issues in their first years of production, the "next year's" clutch spec would be the more heavy duty item (as in spec'd for SNOWPLOWS).  And THAT did happen with the 1988 C/K GM pickups, in the 1989 parts listings.  "Snowplow"?  I thought.  Until I saw a mounted snow plow on the front of a 4wd pickup.  The plow blocks air across the full front of the vehicle, a few inches in front of the front bumper.  When I saw that, it made sense.  And those OEM "snowplow" fan clutches were BEEFY in physical size.

 

One other issue CAN be the type of thermostat being used, NOT just the temperature rating.  The (what I call) "Robert Shaw"-style thermostat (has the three supports on the center section) is supposed to be of a better design for more stable operation.  I believe you can now find them in the Mr. Gasket selection.  Supposed to have better fluid flow characteristics . . . if that matters.  Chrysler used them OEM in the 1960s and early 1970s, but then evolved into the normal U-support style of thermostat.

 

It would seem that to mimic the OEM factory a/c cooling system components for the base vehicle might be a reasonable place to start with upgrades.  For a car of the 1950s, looking toward the 1961s or so to see what was changed/improved might be good research, too.  Might yield some "ideas" which could be used on the earlier models?

 

Not only is the radiator condition important, but also the condition of the block's internal passages.  Just mentioning that for the sake of mentioning it.  I seem to recall the issue of the spring in the lower radiator hoses being necessary or possibly not necessary as long as the system was pressurized?  Adding a correctly-engineered coolant recovery system might be a thought, too (with a coolant recovery radiator cap!).

 

NTX5467

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