Need some help...
I have an '82 TA & replaced the 305 with a 350 carb. After driving it for a little while today my radiator coolant overflow started to boil like a tea kettle! My mechanic thinks I may need another fan as the one I have on my engine now is a manual fan from the original 305. Any ideas why this is happening? The thermostat is brand new & don't think it's that?

 

Well its definently getting too hot. I had that prob when my motor was pretty much stock and never touched. The car would constantly get to 220-230 temps and when i turned it off i could see and hear the coolant boiling in the overflow. Fan switch that turns on at 195 instead of i think the factory 218-222 or whatever it is fixed it. That paired with a 180 thermostat My car constantly runs cool and will hardly get past 195 on a hot summer day.

Not sure if the single fan setups on the 305 were not as powerful as the dual fan setups on the 350 cars though. May have something to do with it.

 

Stevo,
My engine is brand spanking new & today was it's longest drive it's ever had. I only drove it for about 1/2 hour & when I brought it home & parked it I could hear the coolant overflow tank boiling like hell! Are these single, manual fans for the 305's not enough for 350's?

 

Im not sure, because the only advantage to the dual fans that i can think of is that the extra accesory fan is for the A/C so you can run the A/C and either run cooler or the same as with the A/C off.

Im not sure if people buy the dual fans to hardwire them both to work or not. The primary fan may just work a lot better then the single 305 fan setups completely. Maybe someone else can come and chime in.

Was a stock fan switch put back into the motor do you know?
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Sorry just thought of something...does your engine even run off a computer? You wouldnt have a fan switch if you didnt have the computer would you? You said you have a manual fan...(not electric i assume) then it runs off the waterpump pulley?

 

It does run off the water pump pulley...no computer...carb engine.

 

Is the air dam still there under the car? Damaged at all or bent all up? Also, is there a fan shroud on the fan? I know, silly questions, but if any one of them is overlooked or there it could overheat. The radiator could also be a problem if it is old or clogged or not flowing well because fins are bent not allowing enough air to flow through for cooling...just a few things to check.

 

Fan shroud is on a in gret shape & new radiator. No air damn though. I have the lower air damn section, but I'm told there are 2 sections of it & I'm not sure if what I have on the car now is the upper section of it? I'll have to post a few pics of what I have when I've got the time...

 

I have the stock 305 fan clutch on my 350 now. Went to Napa to find out about the severe duty fan clutch & they told me I can only use it with a fan blade pitch of 2.5"...does anyone know if this is what was the stock blade pitch because I have the stock 305 plastic fan in there now?
Also, what about just elimanating the fan clutch all together & getting a heavy duty fan with a spacer? I've been told this alone reduces the engine temp by 20 degrees?

 

If it was my car id ditch the clutch fan and install a set of dual thermo fans with shroud, Run one on a 190'F temp switch in the intake and one on a manual switch in the cab.
What temp is it geting to?
I wouldent think high temps would be good for a new engine. If you need any help on wiring a set up i have a basic diagram of how i did mine here:
http://84transam.blogspot.com
If you need to know anything at all just p/m me, Id be happy to help you out.

 

I'm eliminating the fan clutch & running a flex-a-lite fan w/ spacer. I also took out my 180* thermostat & replaced it with a 160*. This with the air dam installed should work...we'll see.

 

I would not do that; that's going BACKWARDS, in terms of cooling effectiveness.

Try a new radiator cap instead.

 

Many friends on another board I belong to told me clutch & elec fans are junk & not sufficient enough for a Chevy 350 motor. The guy where I buy my performance parts also told me the same thing. here what another member wrote me:

You see, what's cool about flex-a-lite fans (pun intended) is that they spin with the motor. Whatever RPM your motor is turning....that's how fast the fan is spinning. So, you will get the maximum cooling effect even sitting in traffic at a dead stop. They have an awesome roaring sound to them as well. Clutch fans will slow down...almost stopping in traffic....and sometimes when they are wore out, they will not spin as fast when going say 65mph down the road. Electric fans kick on only when they are "needed" which is never sufficient for a Chevy motor. Not to mention, it's electric, so the switch has a tendency to fail...and you won't know it until the temp gauge starts getting too high.

 

I know exactly what flex fans do. Been watching people with those drive around overheating cars for over 30 years now.

As far as how many people telling you how great they are on how many boards, that's about like going to lots of Mcdonalds parking lots on Friday nights, and having lots of people tell you the same monkey-spank. The sheer number of people repeating it, doesn't make it true.

A clutch fan is a FAR superior system. It decouples itself from the engine when the temp of the air coming through the rad is below its set point; then hooks up to the engine when the air temp is high enough to indicate that it would like to be cooled. Unlike a flex fan, which flattens out and thereby moves less air as RPMs increase, even if the car is sitting still. Which is why you see so many people with 4WD vehicles on those boards, talking about "I put this big bad flex fan on my rock crawler and it still overheats" ..... welll, DUH.

Think about it.... that IDENTICAL clutch system you've got, part number for part number, was ENTIRELY ADEQUATE on your grandma's 76 455 Buick land barge that she puttered around town at 22.7 mph in on 100° days with the AC on full blast. It's MORE THAN ENOUGH for your car, BELIEVE IT.

Same for electric fans. The stock electric fan system in one of these cars, PROPERLY MAINTAINED, with the rest of the cooling system (radiator cap) also properly maintained, is enough to cool a 400 in one of these cars. I know, I had a 400 in mine for over a decade and nearly 150,000 miles in the deep South. With the stock single electric fan, stock aluminum/plastic radiator, stock fan switch, stock radiator cap, and so on. The only piece that wasn't stock was a Stewart water pump.

The best mechanical fan you can have is the system you've got, with a GOOD WORKING fan clutch, and a radiator cap that holds pressure (15-17 psi); and of course, a water/AF mix of between 50-50 and 70-30. That combination will not boil over until the coolant temp reaches about 265°.

That "awesome roaring sound" is the sound of horsepower being wasted and gasoline being burned needlessly. It means the car is using more gas and going slower than it would with the RIGHT cooling parts on it.

 

Sorry to butt-in, but while I am no expert this seems contradictory to what I have read. A clutch fan, when operating properly, is in its prime at idle in traffic, low speed, etc. As the engine accellerates the clutch disengages and the fan slows and therefore the rushing air from the vehicles speed takes over the cooling duties (way more airflow than the fan can create). The flex-a-lites work in a similar manner but without a clutch to disengage them. The blades are designed to flatten out as the engine speed increases, thereby reducing drag on the motor (hence they draw in less air at speed also).

I upgraded my LO3 305 to a 350 and have had it out on a road course many times without overheating. I am using the stock 1989 single electric fan wired to a adjustable fan control (underhood not in cabin). Granted, the motor only makes about 275hp. I have a friend who is also using a stock single electric set-up but with a 600hp motor. While it definitely pushes the limits for spirited driving, it handles general duties without a problem.

 

That's somewhat true of a centrifugal clutch fan, but the stock fan has a thermal clutch. The fan is freewheeling while the air coming through the rad is cool, but is driven when the air through the rad heats up. Slippage in the hub at speed also limits the maximum speed the fan turns at, which is good for saving some power and keeping the fan blades from escaping through the hood.

Flex fans were at best a marginal idea 40 years ago when the stock fans were directly driven by the water pump without a clutch.

A lot of people choose the flex fan and spacer because it's a lot cheaper than replacing the clutch hub, and then try to convince themselves that it's an "upgrade". It's rare that you get an increase in performance by saving money.

 

I appreciate your reply & info, but I'm going to stay with my original plan. Maybe I'll be alright & maybe I'll wish I had taken your advice...we'll see? I've gotten advice from everything from old-timers who have been playing with 3rd gen's since they came out to 21 yr old grease-monkey, 3rd gen psycho-nerds & the overwhelming majority advice has been to stay away from clutch & elec fans.
I'm definately against elec fans as the switch is just one more thing I'd have to worry about that could go wrong. The hp that you'd lose is about 2hp & probably never even notice?
I'm not a "McDonald's parking lot" rich kid that beats on his car after dumping thousands into it...not sure why you even went there with me? I'm doing my car mostly for show & Summer/weekend cruises, long scenic/highway drives...ect. Everyone has a different opinion & I appreciate yours...I just disagree with it & that's perfectly OK.

 

The "McDonald's Parking Lot" is nothing personal, it's just something of an expression on the board to refer to the kind of advice you get from people who's only source of information is from marketing copy.

Your flex fan will work, it just won't be as effective as a properly working (ie. not tired 20+ year old) stock setup.

Regardless though, if you're venting into the overflow tank, the first thing I would have replaced would have been the rad cap, not the fan.

 

Just to keep things in perspective, a 60/40 coolant/water mixture won't boil at 16 PSI until somewhere around 270 F. Are you sure your coolant is getting that hot?

 

It was boiling hotter than a tea kettle...bubbes & all! And this was only after driving the car about 20-25 mins at no faster than 40 mph on a cool New England day. It was boiling so much I thought something under my hood was still running after I shut off my engine.

 

are you shure youre fans clutch is evan working at all?
Coz that is exactly what my car did when the old fan system didn't work (the ground wire came lose and the fan didn't come on).

 

The fan itself was definately working so I'd assume so...not sure about the clutch itself but all the clutch does is disengage it at certain temps?

 

Well a tea kettle only boils at 212 F.

The two things that affect the boiling point of coolant are the coolant mixture, and more importantly the relief pressure of the radiator cap. Like I mentioned, 60% coolant with a 16 PSI cap is good to around 270 F without boiling over. That's way overheated. You'd have to seriously abuse it to get it that hot.

If the coolant mixture drops to 40%, and the cap doesn't hold pressure, the boiling point drops to about 219 F. The ECM on an FI car doesn't even turn the fan on until 220 F.

Forget all the nonsense that your friends have told you about what "Chevy engines need for cooling". It's what we call around here "McDonalds parking lot monkey-spank". The 383 in my 84, with a completely stock cooling system (rad, water pump, thermostat, hoses, shroud, and clutch fan) doesn't run a degree over 170 F. Not bad for something that was intended to cool an engine that made a third of the horsepower.

 

I see what your saying...if it wasn't working it wouldn't be able to tell the fan when to kick back on, right? Would it be able to work with a non-working engine temp gauge? Way to check this for sure?

 

The fan will always be turning and blowing some air, but when the rad gets hot enough for the clutch to lock, there'll be a noticeable difference in the amount of air moving. You'll hear an increase in wind noise under the hood that will vary with engine RPM.

The temperature gauge is completely independent of any operation of the cooling system. It doesn't matter if it works or not, but it does make it easier to figure out if you're actually overheating or not.

Your boiling problems are probably related to your rad cap. They cost something like $3, so there's not much point in not replacing it anyway. After that if the engine is still running hot, replace the fan clutch if you don't think it's working.

 

well the way it works is the clutch wont ingage the fan till the air around it gets hot enough, The fan will just spin freely. EG you could probley hold it while the engine is spining and it wont rip out of youre hand (I DON'T ADVISE YOU TO TEST IT THO!!!).
so it will look like it is working but it will only be spinning at 1/8th of the engines RPMs.

To test it run the car till it gets hot if you never hear a roaring sound from the fan it probley aint working (you may have to give it 5/8 min before you hear anything).

 

just thought id add
Thermo fans can cool any engine you just need the right CFM for youre app, and if you dont trust a temp switch run a manual one or both.

I understand if you don't like em u don't need to use them but they are sufficient enough to cool a 400HP+ engine if setup corectly.