Technical changing cooling fan -- Updated

I have this 17" fan on my 250 inline Chevy. I am having heating issues setting still with A/C on. On the road it runs 180* all day, set in a line for 4 or 5 minutes it starts climbing but not over 212* according to the gauge. Will a solid steel fan pull more air, and will the 250 pull it?

 

Shroud. !!!

 

Put a Derale fan on it. I used one to eliminate an electric fan. Very efficient.

 

I say shroud and a stock style 6 blade. Mine came from Old Air heavy duty fan. Shroud came from walker. Runs much cooler than the electric fan I had

 

Weird that it would start doing this after being dialed in for so long. Might let it run and watch the fan to see if it’s flexing flat and not moving air now? I’ve had some of the black plastic ones really get out of shape after some years

 

It's been doing this since the A/C was installed, the engine doesn't idle all that fast. It does have a shroud but being in a '37 truck, the shroud and fan are as wide as the radiator. If I have the room, I think I will try one.

 

Yep, you need a shroud no matter what fan you finally put on it. That fan isn't pulling air through even half of the radiator with a 2 fiddy in that truck because the fan sits so low. My 48 did the same thing every time I got in traffic and I don't have ac (yet) Too much of the radiator isn't getting any air through it when the truck is at a stand still and as soon as you hit 20 or so and air hits it the temp drops right back down to just over the rating of the thermostat. That fan still pulls twice as much air as the worthless ricky racer flex fan I had on my 48.

You have right at 396 square inches of radiator surface and 176.7 square inches of fan coverage as it sits. That means the fan only pulls air through less than half of the radiator.

 

I never trusted those fans with the light duty bent tin/aluminum "blades." Saw way too many flatten out way too fast, and too many more that started breaking the bent part at the bends and around the rivets.

Then again, if the cooling system is pressurized, and the temp isn't getting higher then 210, Other then the fan blade issues, I wouldn't be too concerned about that temp. A 230 temp is a different story.

 

If you have the room I swapped the 46’ to a 6 blade metal fan from the dirt track catalog and it took a while to get used to the noise but man it moves air

 

Low mount water pump is an issue, but the 17" fan covers a good portion of the core. I have the radiator moved forward and down as far as I can get it, but space is still tight. I went to the 17" thinking it would pull more air then a similar 15 or 16" I had, but it didn't, poor design I guess.

 

do the towel test first.. if the fan doesn't suck the towel into the grille it's not working... speedway has a nice aluminum blade fan for cheep... like 50 something...I've never seen those flex fans work for anything...and add ac... no way..

 

these move a lot of air and are quiet....and aluminum...


I know i'm not supposed to post about stuff cause I don't know anything but think I know it all...and 40 yrs in business I must have been a sleep...but try the towel... that will tell you whats wrong first ... then fix...


Flex-A-Lite 1215B Heavy Duty Aluminum Cooling Fan, 15 Inch | eBay

 

thats a cool shroud!! bought , or built??? the fan has way enough coverage to make it work....how deep the fan is in the shroud make s a huge differance...I ve seen those flex fans flatten out in the shroud and actually block the air, they cavatate and make a wall of air inside the shroud.... with the towel test, it would suck the towl to the grille ... but not strong... then run up to 2000 rpms and it would drop....

 

I had the same problem with a small block chevy in my 47 aerosedan. The engine, at idle, didn't pull enough air. Added an electric on the front of the radiator with a switch. Never had another problem when cruzin shows or caught in slow movingtraffic again.

 

Is it losing coolant? If not, 212 is not a problem depending on the amount of pressure in the system. The pressure cap raises the boiling point 2-3 degrees per pound.

‘37 Chevys do not have a lot of grill area for air flow, in addition, the engine compartment is narrow and restricts air flow. Check out the amount of air that come out of the hood side louvres while running, they did not put them in for only decoration. I have a similar Flex-a-lite fan with a shroud and it seldom goes over 205-210 with ac in my ‘37.

Low idle speed may be part of the problem. Most older cars with a/c had a dashpot vacuum on the linkage to step it up when the a/c is on. If stuck in traffic on a 100 degree day I will put it in neutral and increase the idle.

 

Or you could put a smaller pulley on the water pump.

 

Per the photo, the radiator and shroud look fine for the task. The problem must be the fan. As has been suggested, go with a solid-type fan (no "flex" blades) and position it in the "sweet spot" of the shroud opening. Use spacers as needed to position the fan correctly in the shroud.

 

Not everything is a fan problem. Low speed heating can be due to not enough initial timing advance. The radiator pictured has a lot of fins per inch which can restrict low speed air flow.

A lot of differing opinions about cooling systems and fans in particular.

 

Put a real fan on the car, I use a steel 6 blade fan and they keep my cars cool, I have been in bumper to bumper traffic with the air on and the Deuce sedan never ran hot. HRP



Got it from Summit. HRP

 

I second this method. These fans pull a ton of air. And agree with above suggestions of a shroud.

 

212 sounds dang near perfect

I like the standard 4 blade OE fans

 

this is the cheapest solution. there is a small water pump pulley GM made under 6" .

 

Like other have mentioned
Experiment with
Fan
Pulleys
Timing
Stat changing up & down
Pure water cools better lower boiling point , then antifreeze Higher boil less effective heat exchange .
Fan to deep in shroud or not enough,
Shrould not sealed well .
Jag clutch for fan is shortest Oem made.
Also , if you where to add 3 more temp gauges on Gen 1 Sbc in different location , Now you will have 4 different readings.
My self I run Water, spring to Fall
15-20 degs cooler

 

Problem is with the space between water pump and radiator, I don't have any! There is 2" from the nub of the water pump to the radiator fins, and a little more then that back to the balancer. This is a stock 250 engine, not a high rpm killer, while idling very little air movement can be felt around the engine. It won't hold paper to the grill at idle.

I going to have about 1/2" from fan to radiator with one of the solid 6 blades, this will also put the fan about half into the shroud, and if I step down from 17" to 16" I will have roughly 1" clearance around the fan, as it is now, there is about 1/2" clearance with the 17". I used the flex fan because most of the blade is on the back side, the steel fans 75% of the blade is in front.

My water pump pulley is a #3900434 ( '65 - '68 Chevrolet ), 7" diameter. My balancer is a dual groove with 1/4" spacing, there is also a dual groove with 1/2" spacing, I have a 5 3/4" diameter water pump pulley for the 1/2" spaced damper ( space between the belts ).

A smaller pulley would help a bunch, I don't know much about the Chevrolet engines so if you know of a pulley smaller then 7" with the same spacing as the 3900434, let me know.

 

pretty sure the speed way aluminum blade sticks out on the rad. side less than the flex blade you now have... andd can get it in 17'' or 16''

 

a pic of what it looks like all together would help...

 

Sold in Quantity
Each
Blade Count
6-blade
Rotation
Clockwise/Standard
Blade Material
Aluminum
Hub Material
Steel
Overall Thickness
1.88
Hole Diameter
.625
Fan Quantity
Single
Fan Diameter
15 Inch
Fan Flow Type
Pull
Blade Type
Non-Flex
Maximum Fan RPM
8000 RPM
Hub Finish
Powder Coated
Blade Finish
Powder Coated
Blade Color
Silver
Hub Color
Silver
MFG. Part #
1215B
GTIN Code
088657809337
Slot Width
.337
Slot Length
1.23
Weight
3.0
Notes
# 102122

says it's only 1.88 thick...

 

If this is a new condition, have you flushed your cooling system? It might seem like an airflow issue but could be just your cooling system not operating as intended when there's higher thermal load? I've fixed several cooling issues with a diy cooling system chemical flush.

That said, I did have a similar style fan on my 62 Bel Air and went back to the stock style fan and thermal clutch, it moves a lot more air.

Disclaimer that I didn't read every reply in detail.

 

It's an on going issue since adding a/c. Pretty sure it's related to the big water pump pulley not turning the fan or pump fast enough. The balancer is slightly smaller than the water pump pulley.
Not sure how hot it would get if I just let it go on idling.
I am doing everything I can to not put an electric fan on it, the radiator is as far forward and as low as I can get it. If I take out the 1/4" spacer at the fan, the blades hit the balancer. other option is to move the engine and trans back and shorten the driveline, not sure I'am ready for that yet.

 

Yeah it gets tight fast doesn’t it.

out of curiosity if you start the truck and let the ac run with it idling in park in the driveway does the heat creep the same as sitting in gear in traffic?

a different pulley is sounding like the least intrusive solution