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Fan Shroud Bypass Flap?

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Old Feb 28, 2006 | 10:09 PM
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Default Fan Shroud Bypass Flap?

I have a flap on the bottom of the fan shroud on my 80 L82. It looks like someone cut out a section then reconnected it with hinges. What this does is allow air to bypass the radiator. With the way C3's have problems cooling, I don't understand this flap at all.

Has anyone else ever seen this? Please tell me it was just some YAHOO having fun with his new jigsaw.

One other question. My 77 and my other 80 have seven-blade fans. The L82 has a five-blade which aren't equidistant from each other. Which fan is better?
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Old Feb 28, 2006 | 10:12 PM
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It allows you to remove the fan shroud without pulling the radiator, the upper control arm mounts get in the way. Unbolt it, fold it and pull it out.
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Old Feb 28, 2006 | 10:19 PM
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Don't the upper control arms interfere on either side of the fan opening? This flap is forward of the fan, on the bottom of the shroud.
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Old Mar 1, 2006 | 08:07 AM
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ahh ok, in that case no idea, bubba would be my guess. Maybe he had a habit of droppin stuff down there
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Old Mar 1, 2006 | 08:58 AM
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The flap was used in conjunction with the electric fan. The fan provides engine cooling at low or no speed. The flap would open at higher speeds when air flow through the radiator was sufficient for engine cooling. The air flow through the flap was for engine compartment cooling. By the late 70's, engine compartment temps were soaring and everyone knows about the heat in the passenger compartment problem.
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Old Mar 1, 2006 | 09:34 AM
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The flap was to release pressure at high speed. The 7 blade fans pull more air & neither the 5 or 7 have the blades equidistant.
L-82 W/ A/C 7 blade or 5 blade + aux. el. fan, depends on year.
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Old Mar 1, 2006 | 11:14 AM
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Originally Posted by PairOf80s
...I have a flap on the bottom of the fan shroud on my 80 L82...Has anyone else ever seen this?...The L82 has a five-blade which aren't equidistant from each other. Which fan is better?
The flap is OEM with the '80 L-82. You should also have an auxillary electric fan. You should check the '80 assembly instruction manual (AIM) for the correct fan. The original part number will be listed and (probably) an illustration. Off the top of my head, I can't recall whether my '80 L-82 has a 5 or 7 blade fan.
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Old Mar 1, 2006 | 07:43 PM
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Default 80 Radiator shroud

I recently parted out a 1980 L82 and have the very same shroud to sell.
Clix
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Old Mar 5, 2006 | 01:54 PM
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Thanks for all the info!! What a great website!
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Old Jan 18, 2017 | 11:55 AM
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I figured it would be better to bump an old thread than start a new. But boy I am I having a hard time wrapping my head around my '79 cooling system.

At highway speeds, with that super dense A/C condenser and the flap at the bottom of the shroud wide open, I don't see how any air is really moving through the radiator.

My only thought right now is that my electric fan, which does operate, but not well, performed at a much higher level when new.

I just ordered the SPAL 006 electric fan kit. I hope that it will bring the setup back to factoryish cooling. Hopefully better. Because right now I'm overheating, with all new cooling components.
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Old Jan 19, 2017 | 05:47 PM
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Is your engine a stock L82? If not what motor or major modifications?

Do you have both the valance AND its plastic extension installed under the front end? Without both air will not be directed properly.

The radiator is also surrounded by closed cell foam pieces. Closed cell foam both fills gaps and stops air movement. Are yours present/intact?


Also define "overheating". If you have the stock temperature gauge notice that TDC is 220F instead of the FAR more common 200F. By design the stock cooling fan doesn't turn come on until the temp reaches about 238F!

I'm fairly certain that the auxiliary cooling fan was intended to kick in only at idle/very low speed with A/C running in very hot weather. This is why it was only included with A/C equipped cars with the L82 engine.

I also have a '79 L82 and while I know that the fan works, I don't believe it has ever come on during driving. While I live in a very hot climate I'm far from traffic jams and enjoy spirited driving on winding, hilly, rural roads. At interstate speed (WELL above the 55mph limit when our cars were new*) or repeated wide-open throttle events during hot weather I have seen the temp gauge creep up above 220F (top center gauge) but it hits a ceiling around 230F. I once thought my temp gauge was off and the electric fan was kicking in but I lightly taped the blades in place to find it intact after such a run. During normal driving at speeds rarely above 55 mph and regardless of outside temp my gauge rarely goes above 200F.

That crude looking spring-loaded door in the shroud looks crude because it was a modification done during the assembly process. It was discontinued (in 1981 I believe) when the engineers found it had little or no effect on engine cooling.
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Old Jan 22, 2017 | 01:42 PM
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I have dual Spal fans and the accompanying shroud has many rubber flaps...roughly 2x3" in size.....at 20 mph+ surely they are open....but they suck closed with the tight shroud and install I did.....I note that the fans turn off about 40 mph even with A/C on.....but that's the FI computer programming..... Spal fans suck, real good.....

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Old Jan 31, 2017 | 12:23 PM
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Originally Posted by SwampeastMike
Is your engine a stock L82? If not what motor or major modifications?
As far as I know, just intake/exhaust engine wise. But it is loud as hell (good), and loves to get hot. But I also believe that the rear end has been swapped out for a much higher gear. The car will do an actual 70 mph when it is indicating 80 mph. Which puts a 70 mph cruising speed running at a whopping 3250 rpm! (I hope to put a 4 speed overdrive trans in at some point to deal with this)

Originally Posted by SwampeastMike
Do you have both the valance AND its plastic extension installed under the front end? Without both air will not be directed properly.
Thanks! for responding. Luckily I am slow to respond because I've been getting some work done on the car. I do have the valance, but nothing "vertical" attached to it. Which certainly explains why I couldn't understand the design before. I appears that on a '79 L82 w/ AC I should have a "HD" setup including both of these parts:??

Spoiler


Extension



Originally Posted by SwampeastMike
Also define "overheating". If you have the stock temperature gauge notice that TDC is 220F instead of the FAR more common 200F. By design the stock cooling fan doesn't turn come on until the temp reaches about 238F!
Having replaced radiator, cap, thermostat, water pump, and still watching the needle just keep climbing past the overheating zone I convinced myself that as long as I wasn't blowing the radiator cap then I must be fine, possibly bad temp sensor. That was until I came home and could hear the loud as can be boiling inside my overflow reservoir that went on for about 15 minutes or so!


Originally Posted by SwampeastMike
I'm fairly certain that the auxiliary cooling fan was intended to kick in only at idle/very low speed with A/C running in very hot weather. This is why it was only included with A/C equipped cars with the L82 engine.

I also have a '79 L82 and while I know that the fan works, I don't believe it has ever come on during driving. While I live in a very hot climate I'm far from traffic jams and enjoy spirited driving on winding, hilly, rural roads. At interstate speed (WELL above the 55mph limit when our cars were new*) or repeated wide-open throttle events during hot weather I have seen the temp gauge creep up above 220F (top center gauge) but it hits a ceiling around 230F. I once thought my temp gauge was off and the electric fan was kicking in but I lightly taped the blades in place to find it intact after such a run. During normal driving at speeds rarely above 55 mph and regardless of outside temp my gauge rarely goes above 200F.
Great info, the car wants to get so hot I had figured it had been modified internally, even though the seller said it had not. (Just has a edelbrock air cleaner intake and open flow exhaust) I now think it is running as intended, just not getting the airflow that was meant to get to the radiator. I did get the SPAL 006 fan installed. Looks/works great, and surely I won't regret installing it since the car is in South Louisiana.

Originally Posted by SwampeastMike
That crude looking spring-loaded door in the shroud looks crude because it was a modification done during the assembly process. It was discontinued (in 1981 I believe) when the engineers found it had little or no effect on engine cooling.
Is there a consensus on what to do with this door? I put a lot of effort into bringing it back into operating condition (it was just zip tied on one side). But I'll close it or open it up if that would help. Thanks again for all the info.
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Old Jan 31, 2017 | 05:27 PM
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Kingpen, you are correct that a 79 L-82 with A/C should have both, if it doesn't have a pace car spoiler.
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Old Feb 1, 2017 | 02:16 PM
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Originally Posted by C3 4ME
Kingpen, you are correct that a 79 L-82 with A/C should have both, if it doesn't have a pace car spoiler.
Excellent! I got them ordered from Eckler's this morning.
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Old Feb 13, 2017 | 09:01 AM
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Originally Posted by KingpenM3
Excellent! I got them ordered from Eckler's this morning.
I got everything in and installed. Car still wants to run up in the 235 degree range humming down the highway at 70, but it stops and holds that temp now.

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