Hi Aldo, now that you have all the books I'll soon be asking you for answers. It's great to see a young man with a thirst for knowledge and as the years go by other new owners will have a person to ask for information.

The clutch fan works off temperature not rpm. There is a bimetallic coil and two fluid reservoirs inside the clutch.
When you first start a cold motor the bimetallic coil is in the start position and the fluid is in one chamber.
This lets the fan turn withsome slip.
As the motor warms up the coil moves which allows the fluid to go from one chamber to the other.
Now the fan will haveless slip.
When the motor cools a little the fluid moves again, and you get more slip.
If the motor starts to get too hot, ( somewhere above 180*-190* ) the fluid will automatically go back to the other reservoir and make the fan turn faster, again,less slip.
When you a cruise down the highway, and the water temp is low enough the fan slips and the air being pushed thru the rad is keeping the temps down.

Auxiliary Fan: If the book says on at 238*F and off at 201*F then start there. Others may have found a better way, but untill then, go by the book. Adjustable switches may be expensive, but you can fine tune them if you want to.

Talk to you soon, PG.

 

PG, when you first start, isn't the clutch engaged until the centrifugal force forces the fluid out? The reason I thought this was when you first start up a cold engine, there's a tremendous amount of fan noise (roar) for about 30-50 seconds and then it gets quiet.

 

Aldo,
I agree that the temp that the aux. fan comes on at is way too high. Prior to the weather getting hot, which is the middle to end of March here, I'm going to do something about that aux. fan in my car. It also seems not to do much of anything.
pg,
The "fan clutch" details were great. Good info.
Rick,
That fan system sounds like the way to go. I like the fact that you can set the temp for the fans to turn on. Even w/ the cost of the new alternator, in the long run, that's the system to solve all the fan problems.
Funny to say, but I didn't even know that I had an aux. fan in my 'Vette for the first three months I had the car. I happened to see it when I was checking everything one Sunday. It's really burried and out of sight to say the least.

 

Hi 73shark, I only know the basics about the clutch fan but that is probably how it resets itself.
You could try a test, see how hard it is to turn the fan before you start it and then see if there is less resistance after 30 to 50 seconds. PG.

 

PG, thanks for the explanation about how the fan clutch works.
I'll check if mine works properly when the engine is hot

about the auxiliary electric fan , I bought a 30A switch to start-stop manually the fan. Now I have to find a suitable place in the cockpit to place it ( I think near the fuse panel).

I hope the auxiliary fan will do a good job when hot weather will come.

It seems that this auxiliary fan has became standard on 81-82 corvettes , because the related engine switch-sending unit is available on catalogues only when searching for 81-82 models. but my 79 books ( assembly and shop manual) have this auxilary fan described...

I hope my engine +aux fan will do a good job. If I have to spend good $$$ for improved cooling , I think I'll never go for dual electric fans but for an aluminum radiator ( if it really works great as DV8 says).
the dual electric fans are a loss of energy in respect to the engine fan , because there is 1 energy conversion more ( with energy loss) from mech to electrical and mech again.
the aluminum radiator , if effective with the standard engine fan, improves cooling without any energy loss and being aluminum made , I suppose it to be lighter in respect to the standard one, so some lbs less on the front of the car too.

 

Hi Aldo!

Here's the straight scoop on engine cooling as I have learned it (the HARD way!).
Aluminum radiators cool better than copper & brass units. They have better water and air flow characteristics and shed the heat better.
Electric fans are more desireable than engine driven fans where horsepower is concerned. Electric fans place less parasitic drag on the engine and this gives you more horsepower.
Engine driven fans are not subject to burning out or other electrical problems and are considered more reliable - as long as your fan belt doesn't break. For this reason some people prefer engine driven fans.
Your theory about power loss (degradation) from the alternator converting mechanical energy to electrical energy is correct but not fully applicable when factoring horsepower gain/loss.
The race car drivers remove their engine driven fans in favor of electrical ones for weight savings and horsepower gains. The show and go guys like to put in electric fans for the WOW! factor. I used to have an electric fan and adjustable thermostat set up in addition to my engine driven fan but after I put in the aluminum radiator I ended up removing the electrical components.
If you guys haven't guessed by now, I SWEAR by my aluminum radiator. I knocked my brains out (and my wallet too) trying to correct my cooling issues. The universal fit aluminum radiator was the best money I ever threw at the problem.
The only other thing that needs to be stressed about cooling our C3's is air flow. C3's are bottom breathers, meaning that they get air from under the front of the car. Air is then directed up over the face of our "back tilted" radiators. The problem is that the air wants to go up and over or around the radiator instead of through it. Our job is to seal off all of the air gaps around the radiator where it meets the radiator support and also the top of the radiator support where it meets the hood. This will force the air to go through the radiator instead of letting it bypass the radiator. Those of us with stock hoods may still find the factory installed foam rubber air dam on top of the radiator support but I figure after 30 + years they may have rotted or fallen off.
I did 2 things, first I ordered a radiator seal kit from Doc Rebuild and installed it, second and probably more cost effective, I bought a tube of 3M weatherstrip adhesive and some soft foam rubber pipe insulation and made my own supplemental air dam because I have an aftermarket hi-rise hood. I just kept on adding layers of soft foam rubber pipe insulation until my hood started to compress it in place. Here's a picture of my supplemental foam rubber air dam along with some of the Doc Rebuild pieces. You can see the compression marks from the twin turbo hood scoops (NO, I don't have turbo's - YET). The 3M weatherstrip adhesive is an awesome product too, easy to use and works great!
As stated in an earlier post, some of the small pieces of pipe insulation that you see are just cushions protecting the aluminum radiator while I was trial fitting it.




[sm=icon_cheers.gif]

 

Hi there

quite hot day yesterday . Out with my Vette with T-tops off. great!

I have placed the aux fan switch . it's a quite large switch+related fuse. the aux fan works great and seems to be able to keep the temp low.

If i go quite slow ( 1500-2000 rpm)the temp remains far below 180° , but If i go a bit faster for a while ( 3000 rpm) the temp quickly reaches 200°. I have still to check if it can exceed 200°...
Anyway the aux fan seems to help a lot. I suppose that when weather will be really hot , this aux fan should be kept very often ON to cool the engine.
Let's see...

I miss some foam gaskets on my radiator. I think I should put them in place soon
Should I go for a 160° thermostat? or keep the OEM?

In hot days , I think I'll drive my car always with T-tops removed. I think it's the best way to live with the high Corvette heat

The Corvette puts out an incredible amount of heat from the headers! yesterday I met a Mustang 66 and we were there watching at our cars. The Mustang was not so hot as my Corvette ( we have about the same tunings : various Edelbrock parts, steel headers...)
I think one of this days I'll try a drag race with this Mustang. I'm curious to see who wins...

[IMG]local://upfiles/6949/97BE4E2B920C4D658B82A1B559BBEA28.jpg[/IMG]

 

Aldo,
My opinion, with the hot climate where you are, go with the 160 degree thermostat. I find that here in Texas, it's the only way to go. If you want, for the winter months, to go back with the 180, that's cool too, but for the hotter months, keep it cool with the 160.

 

I remember reading a long time ago that most thermostats were only accurate to + 20%. Now they may be better than that now cuz my new Tahoe has a 200 stat and that's what the gauge reads.

 

Hi Aldo, to take a ride with the T-Tops off is just too much fun. I think the C-3's look best with the tops on, but from the inside, windows down and tops off is the best.

You did a nice job with the aux. switch, very neat and out of the way but easy to get to.

Not sure why 79 needed both water pump fan and aux but there must be a good reason.

Gaskets on the radiator were explained in depth by DeeVeeEight, do what he suggested, it will make a world of difference, I used a lot of heavy foam to block every opening, you said some is missing on your car, fix that first and see if you haveany improvemet.
DV8 went thru trial and error and found that the aluminum radiator solved his problems, you may try to remove and boil out your copper rad just to see if there is any improvement, but bottom line aluminum is better.
As far as the T stat, try a 160* if you want, this has been debated to death and since it is cheep and easy to change, go for it. Here in North Carolina we had a record of 100* days last year and my car never went over 200*, maybe the Vette owners in Canada have to worry that there car will run to cold, but not here and not in Texas. Just get a fail safe.
Its spring here and the temps will only get hotter as the months go by, What is it like in Italy now?
I bought my car in November and it was hot inside then, whenit got to spring, I thought I would die in there, the PO replaced the heater hoses but eliminated the heat shut off valve, replacing that solved some of my heat problems, also there is a boot at the transmission shifter, if that is bad it lets in a lot of heat at the shifter, see if that is good.
Lets refer back to what DV8 posted about cocpit insulation, again he posted some great tips, read them and apply them, it will help keep down the heat and make for a very enjoyable ride. I bought and installed the transmission foam and collar, how much does it help, I don't know, but it can't hurt.
Last word, It must be such a head turner to have a C-3 in Italy, I looked at the pictures that you posted and the other cars are so small, I can't go for gas without spending time answering a million questions, poping the hood and hearing some story about how they always wanted a Vette or that therefriend owned one, and to find a 66 Ford over there, thats just great.
Don't race him, just tell him that you need some real compitation, and laugh at him.
Have a great day, you are the only person I know in Italy! Best to you, PG.