Finally found a fan that keeps my 69 400 Firebird cool
 

I've been struggling with high heat at idle for a long time and none of my attempts to solve it have ever been a complete solution.

FYI, I have never had a heat issue while moving at +20mph, only under and especially at idle on days over 75 degrees. I have managed to sneak up on it by changing to an aluminum radiator and NOS water pump with cast impeller but the temp would still climb when sitting at idle. I have a shroud and have tried many different flex and clutch fans but up until recently nothing worked as well as my stock 5-blade flex (assisted by a Spal electric push fan), but even with the Spal running my temp would keep rising.

Two weeks ago I replaced my stock flex with a Derale 17019 6-blade flex and so far it has been keeping the heat under control. I run 2800 rpm at 70mph and on the e-way I was at 180-185 degrees. At idle the highest I went was 200 on an 85 degree day in direct sun and when I engaged the electric fan it went down to 185. The ultimate test was at the Woodward Dream Cruise where I was idling in heavy traffic for long periods of time and never went over 200 degrees.

I am in Boston and we have horrific traffic, I upgraded to a Cold Case and it definitely helped but still had issues in heavy traffic, a little longer and I would have had to pull over.

So, are your results with the spal fan and fan clutch? or just with the new Derale flex fan?

Mine warms up at idle...thx for this

Years ago when I had Pontiacs that ran hot, be it a race car, or street car, my go to fan was a nylon 18.375 diameter fan. It pulls more air than any fan I've ever used at idle, and all the way through the RPM range. The fan blades are almost 90 degree pitch, designed to pull maximum air.

Link to nylon fan: https://www.summitracing.com/parts/flx-104465

Dirt track Pontiacs are tough to cool, but this fan was recommended to me by the shop owner that I used to send all my radiator work to. I tried one, and was sold. Another nice thing is they are much lighter than a fan clutch assembly so easier of water pump bearings also. They aren't going to get you any fuel mileage improvements, but keeping the engine cool trumps fuel mileage.

The clutch fans I tried were the worst.

My results were:

200 max with the Derale only.
180-185 with the Derale + electric push fan.

With any of the previous fans I used my temp would continue to climb until I either got moving more than 20 mph or pulled over and popped the hood to cool it off.

Oh wow, that's excellent, and that nylon fan is pretty cheap so it's definitely worth a try. I did a bit of poking around and I see that there is another one that is a re-branded version of the Flexa lite for a few bucks less and is called: Allstar Performance ALL30095. I think i will pick one up just to see how it compares to the Derale. Thanks for the tip!

:welcome:

Not sure if this is something you can offer; however, for a street application do you have any idea about noise the nylon fans produce? I've used other flex fans (stainless blade, steel) and there is a definite 'roar' when the engine revs and it seems to be a draw on the pulley system.

I used it on several street cars, I've never found the noise overbearing, or objectionable.

You may not be old enough to remember cars before many bladed clutch fans, but direct drive fixed fans never sounded like vacuum cleaners. The loud noise seemed to come about when clutch fans became more commonplace. At $35 you can try it out without a huge cash outlay, but I really don't think you'll find the noise a problem.

The original use for the nylon fans were RV applications, it worked so well for RV applications performance car owners were looking for a inexpensive simple no frills fan that moved a ton of air, and this fan fits those needs very well. As I said, my radiator repair shop owner is the one that first told me about these fans, so he was using them on daily driver cars, not high performance applications. If they were objectionable for a quiet daily driver, I'm sure he wouldn't have been installing them.

Remember that heat travels at the speed of electricty, electrons is how heat transfer is accomplished. The more air that crosses the heat exchanger (radiator) the quicker heat transfers to the atmosphere. Move more air, move more heat. Pontiacs had fixed fans for decades before the clutch fans came along, the belts, and pulleys can handle the loads. I've used these fans on race cars for years without any sign of a problem, if they can stand that type of abuse, you're not going to overstress anything on a street car.

I hope that helps you out.

So many variables related to cooling, but if you have an aluminum radiator with a mechanical and spal electric fan and just barely getting by on a 75f day, there is something else causing the high temps, these cars didnt overheat when new on stock cooling parts, especially in 75f temps.

Have you checked other things like the tune of the carb/engine? Water pump to divider plate clearance? right size pulleys? lower rad hose not collapsing? 180-160 T stat?

I have 2nd gen firebirds, 2 with stock radiators and pumps but running about 100-150hp over stock, and 1 with a 500+hp stroker engine, all cars run right around the 180 T-stat temps in any driving condition or drag racing, nothing special on any of them, stock 4 core radiators on 2 with worn out stock clutch fans, and a 3 row budget aluminum radiator on the stroker car with a worn out clutch fan... can drive them in 90f temps with 80% humidity and none go over 190 idling or at 65mph.

Just a suggestion to look into other aspects of the car/engine than focusing on fans as a band aid, you should have plenty of air flow with a good stock fan/shroud and especially with the added electric fan.

stock flex fan or stock fan?

Not sure who this question was for, I stated what fans I use and the OP stated what he has...

Freebird69, few questions...

the 5 blade factory flex fan that was replaced, was it mounted to a shallow depth fan fan spacer & an original style 4" hub height 1969 11 bolt water pump? Or does your engine have a later TALL style 11 bolt water pump. I'm assuming your Bird has the factory fan shroud.

cooling journey
 

I admit that cooling my car over the years has been fun.
what i can say is all the parts must work together.
Mine barely hits 170 thermostat unless on highway when temps are over 85-90.
Using the following
Cold Case Aluminim Radiator(2 rows 1.25" tubes)

AC style pulleys to overdrive fan and Cooloant(major improvement at idle!!!)

When overdrive pulleys were installed the 5 blade factory fan became noisy(more RPM)
it now looks great as garage art along with original Crank and WP pulley)
Also have 11 bolt pump and timing cover installed with tweak to divider plate.

installed 7 blade AC fan from 76 TA found hayden STD duty fan clutch worked fine(tried HD and SD)

HEI curved conservative 10 initial 32 total(comes in at 3500, Heavy HEI springs)) 14 from VA on ported.
Qjet i rebuilt with parts from Cliff, no issues.

NOS Delco thermostat 170 that actually cracks open at 165, fully open at 180.Checked on stove before install.(superstat worked well as well)no holes drilled in stat.

no issue with trans cooler use in radiator as well.

mine runs just under 170 when cruising around and NO increase while stopped in gear.
much of this knowledge came from research on this forum.

Good Luck
Gerry

Hey Gerry. Just out of curiosity, where are you measuring water temp? Thanks.

temp sender
 

mechanical gauge with sender in crossover near thermostat, actually port behind alternator.
That is factory location for sender in 68. The other spot in crossover is for TVS.
Wanted to add I have lower air dam and all seals that go around core support so all air goes thru radiator and use
the original factory shroud.
I have become more impressed with original GM parts thru the years.
Also fan blade shape truly effects possible noise level.
she also knocks down 16-17 MPG!!!

Gerry

Thanks Gerry. Looks like a really nice car.

Oh yeah, I've been through the entire tune and cooling system. Stock NOS pump with cast impeller, good divider plate clearance, stock shroud, etc, etc.

My car runs cool while it's moving so it's an air-flow problem while sitting still. Under normal driving conditions I have no problems but I live in an area where traffic can be heavy so stop and go traffic is an issue. I know there are many Pontiac owners that struggle with heat so I am not alone and that's why I started this thread.

My car has the short neck WP and the fan sits right where it should in the stock shroud. I don't recall the spacer length that got replaced it when I installed the aluminum radiator (which made no difference from the stock rad).

Also, I have the upper and lower baffles installed and a gasket around the front of the rad to keep air from sucking in from the gap.

One thing that I did not mention is that this is an AC car so there is a condenser in front of the rad that I'm sure does not help with air flow.

Wow, runs cool AND gets good gas mileage. I'm jealous ;-)