I'm putting a new 350 with a brand new flex fan, aluminum water pump and radiator in my vette, and I was just wondering if it will cool better than stock.

I read up somewhere that stock c3s are prone to overheating in heavy traffic and in stop-and-go situations. So I feel like an aluminum radiator and water pump would prevent that, but im not sure.

 

Flex fans are not the best. The stock clutch type fan is the one to use.
A new, better radiator should help.
As far as a aluminum water pump, I doubt that al vs cast iron would make any difference, except for weight.

 

I read many articles about Flex Fans...improved airflow seems to be a problem for them.

 

Have you actually experienced overheating with the car? Generally speaking, GM didn't consider Corvette engines as overheating until they hit north of 230°F. There are multiple elements to get a well-performing cooling system in addition to the coolant flow itself: i.e., timing, effective sealing, proper shrouding, front air dam, etc. The GM fan and clutch is effective.

 

My 2 cents. I've owned a C3 for many, many years. Overheating at idle isn't a problem at all. Motoring up a hill, that's where you make heat.
Yes of course you have no air flow stopped, but then that's what your fans are.
Now of course there are a few options as per fans. The stock fan with clutch is of course a very good option. Electric fans of high quality are also a excellent option. Like OEM fans from a newer car.
And then there is the absolute worst option. You could put in a flex fan. Also known as the fan of death.
It's your car.

 

Well the guy who's doing the setup for me said that the flex fans are good at moving a lot of air at low speeds but they flatten out at higher speeds to reduce drag on the engine.

The car is getting a performance oriented setup, so the less drag the better.

 

Why are flex fans the worst option?

 

Because they use the most horse power to turn. Robbing power that could be used to push your car forward. They run 100 percent of the time. Certainly not needed going down the road at any speed. But your using fuel to turn it.
And if the power loss isn't enough. When those flex fan blades get tired of flexing. They just fly off! And straight through a fibreglass hood I might add. Extremely dangerous.

 

I haven't experienced overheating. I haven't gotten a real chance to test it out since its not quite done yet.

I took it for a test drive earlier this week and it did really good. Temp never got above 180 and it was in the 80s outside. However, I never got into stop-and-go traffic.

 

I feel like they don't use the most power honestly. They're designed to flatten out at higher rpms to reduce drag on the engine. A clutch fan is always engaged. The drag only increases with engine speed for those.
as for durability, youre probably right. I did get a really well built one that's stainless steel construction so maybe it won't be so bad

 

Lots and lots of testing has been done as per cooling fans.
Flex fans are for a budget minded individual who is going to flip the car straight away.
where power and fuel economy are not a consideration and there is zero concern for longevity. Then the flex fan is the one.

 

When I first bought my c3, it had a stock radiator, flex fan and no shrouds.
surprise surprise it would overheat at idle and low speeds.
the flex fan will not make up for an old radiator and no shrouds.
I replaced the radiator with a 4 row aluminum, still got the flex fan and no shrouds but the temp never budges off 165.
i have sourced an original 7 blade fan with clutch and original shrouds that I intend on replacing the flex fan set up with.
so in my opinion, a flex fan is not a solution to overheating problems. If you go overboard on the radiator, you’ll be fine with either.

i think the power loss is minimum. Idk how much power your pushing but the maybe 10-15hp isn’t a huge deal if your making 400. Maybe it is if you’re only making 250. I’ve taken my flex fan to 6300rpm more times than I can remember and it’s never flown apart.
Eventually when I swap my fan setup over to stock I’ll compare the difference, if any, in my 1/8 mile times.

 

Yeah the engine thats in there now is making at least 385. Its based on a crate engine offered by GM. It has a bigger cam than the crate though and it also has ported heads so its probably closer to 400 hp.

 

I have a 427 that is in a 1968 C3 and my car started life with a solid lifter engine. I built the engine to copy the L88 engine design and it worked okay until it came to heating up to over 240* with cast iron heads. I started to experiment with my options.

I ran pure water, 50% and 30% anti-freeze and even a mixture known as NPG made by Evans. The biggest thing that made a difference was the radiator seals and sealing to the hood as well. After getting the radiator sealed well the temperatures came down a bit. I switched it to Flex fans with factory radiator and saw no real difference. I used this configuration until I switched to a BeCool radiator for the 1968 with a 4 speed. The temperatures did not drop that much after changing the radiator. I was expecting a substantial temperature drop with the new aluminum radiator.

Then I tried adding a bottle of Redline's Water Wetter and the temperatures did drop by 10-15*. Two bottles of water wetter and pure water worked the best for transferring heat out of the engine. I switched to 70% water and 30% anti-freeze and my temperatures went up instead of down. 50% antifreeze was even worse as the temperatures kept climbing.

Then I went to the electric fans, I ordered a shroud with 2 SPAL 11" electric fans designed for the BeCool Radiator and it worked well right out of the box. In traffic the temperatures started climbing even with the fans running 100%. This time I pulled the fan shroud and sealed it more effectively to the engine compartment and the temperatures dropped and it can hold which is a win. The fan shroud needs to be very carefully sealed to the engine compartment to be sure that no air is able to go around the seals and through the radiator. For me the biggest seal leak was on top of the radiator so I used a harder foam to construct one for testing.

One aggravating factor that I was unaware of was that my vacuum advance mechanism was not working properly. This kept my engine running a bit retarded and this makes extra heat. Be absolutely sure that your distributor is working 100% properly before taking on any heat issues.

My Flex fans never lost a blade or anything but once I did loose a nut off the flex fan attachment point and it promptly punched a hole in my new radiator. It only cost me a new aluminum radiator.....

 

you write "NEW" 350.
? Is that brand new never run block? Or a rebuilt motor?
? If not brand new, was the used block either vatted or baked&blasted in prep for rebuild? If not, you should perform a heavy duty chemical cleaning of entire cooling system (including block, heads etc). Don't know don't count; find out.
.
Pass on the flexfan; they're usually noisy and any failure's usually catastrophic. Instead use a good quality, New fan clutch and OE-type fan.
? When New, did your car have an OE chin spoiler? If yes, is it still in place ? They make a lot of difference, even at low speed.
Same for all fan shroud pieces and foam seals etc.

 

The 350 is rebuilt for performance.
I would assume it was.

I've been assured by the guy doing all of this for me that the flex fan he's using is a high quality durable stainless steel fan. I'm very confident he knows what he's doing as he's been doing performance engines himself since 78. With proof to go along with it.

I'm assuming the car did have one new. I'm pretty sure all did from the factory. It doesnt have one anymore as the fiberglass where it bolts to the car has been damaged. You can no longer put an air dam on the front.
so far, the car has stayed cool with the new components. In 80 degree weather, on and off the highway for about 20 minutes the car never got above 160 or 170. It slightly rose above 160 when I started getting on the gas. But it never even got close to 200, even at low speeds.

 

Your car. Do what you want.

However that flex fan is not the best choice. A 20 year old thread about fans.

https://www.corvetteforum.com/forums...lutch-fan.html

Fix the fiberglass and run a proper spoiler plus clutch fan. At speed, the clutch will disengage since you don’t need the fan.

I personally run an electric fan and it never enters above 40 mph even when it is 90+ outside. And I have a 496 big block.

Also sounds like your engine builder used a 160 thermostat. Lot of people thinks that helps performance. But it increases wear on the engine. These engines were designed to run 195 or so. I run a 180 thermostat and my fan is set for 195 on, 185 off.

You said your engine builder has been building engines since 1978. A lot of ideas that folks had back in 1978 have been proven wrong.

 

Pass on the flex fan ( JUNK ) !

 

There is not a one size fits all for engine coolant temps and performance.

There has not been enough information provided to deduce that the OPs ideal coolant temp is 195. We have zero information on compression ratio, timing, cam size, fuel being run(gas/methonal/ethanol), fuel delivery(carb/efi), power adders(NOS/boost)
All we know is it is not a stock 350 from the 70s.

The OP should do his own research, discuss with his builder and make an informed decision to what’s best for his case.

 

I’ve been around for a long long time.
I was around muscle cars when the first aluminum and fiberglass flex fans first came on the market.
At the time the big selling point was that they reduced weight on the crank because they eliminated the heavy clutches and in doing so they would allow the engine to rev faster.
Better cooling wasn’t their purpose, but since the clutches were eliminated the flexibility of the fan blades was to replace the function of the clutch.
Back then another selling point of the flex fans was that the factory fan clutches had a higher rate of failure than today’s and with a flex fan the clutch was eliminated so you never had to worry about the clutch failing.
They were a big hit with the motor home owners.
They worked well, but over the years the quality went down hill and there were reports of the blades coming apart, even more so today.
The new clutches are more improved, last for decades and are somewhat lighter weight than the early clutches.
Now electric fans are all the rage and in my opinion a big improvement over the clutch fans, depending on the application.
In a stock or mildly built engine like the OP’s I would run a clutch fan set up before electric fans.
In a high performance engine where cooling is essential at slow speeds, electric fans are my choice.
Now in my older Jeep and the way I use it the clutch fan set up is way better than an electric fan set up.
If the OP’s car was mine I would use the clutch and fan set up, but it isn’t my car.
The last thing I would use would be a flex fan.