Chevelles.com banner

1 - 20 of 152 Posts

·
Registered
Joined
·
6,367 Posts
Discussion Starter #1
More of a rant, but very very open to suggestions.

I joined a car cruise on tuesday, and while it was hot for local weather, it was only around 24-25C (75-77F) and my car just cannot creep at idle. It got up to 240F (sensor in the manifold) before I had to bail out. The crazy part is I put the car on the highway and at 100 kph (62 mph) I got down to 164F coolant temps. 76F temp climb, I could probably do just as well without a fan.

I have a 6 blade aluminum fan. Oddly it doesn't have any real contour in the fins.
I do NOT have any clutch on the fan, it's bolted to the water pump.
Aluminum radiator, no idea the core count or brand.
Factory GM shroud. - the fan could be brought in closer to the block I suppose, as right now the fan is about flush with rear of the shroud.
Timing is at 18 initial, doesn't make a diff if i change it to 22 or so.
AFR is at 13.75, doesn't matter if I make it richer or leaner.
I have 2 temp sensors, so not a faulty sensor.
Weiand aluminum water pump


When driving and there is airflow, it's clear it will cool sufficiently. It seems there is just no airflow at idle while sitting still.

I think I need to get a different fan arrangement, or could it be possible there is something messed up in the water pump that is preventing it from keeping the coolant flowing at idle RPM?
 

·
Registered
Joined
·
5,590 Posts
As you know Chris most Mech Fans do not do a good job at keeping a BBC Temp Cool enough at Low Speeds/RPMs

Could be the Shape of the Fan Blades or that the Fan Blades are not 1/2 IN and 1/2 OUT of the Shroud Opening/Hole

So maybe just getting a Mech Fan that has some Curve & Bend in the Tips will help plus moving it closer to the Engine
so the Blades are 1/2 In/ 1/2 Out of the Shroud Hole

As you have found out Air Flow is one of the Keys to keeping the Engine running cooler

Another Key is a Rad with as few Rows of Tubes as possible
and if there are other things in Front of it like a A/C Condenser the ability to Pull Air thru them

My Small 2 Row 1.25" Wide Tubes Alum Rad Core that is only 23.5" Wide X 16" High
with SPAL Dual 11" Efans/Shroud keeps my BBC Temp at 180* to 190* in City Traffic
when Both Efans are on in HOT 30+C Temperatures and with a Trans Cooler in Front of the Rad







 

·
Registered
Joined
·
6,367 Posts
Discussion Starter #3
As you know Chris most Mech Fans do not do a good job at keeping a BBC Temp Cool enough at Low Speeds/RPMs

Could be the Shape of the Fan Blades or that the Fan Blades are not 1/2 IN and 1/2 OUT of the Shroud Opening/Hole

So maybe just getting a Mech Fan that has some Curve & Bend in the Tips will help plus moving it closer to the Engine
so the Blades are 1/2 In/ 1/2 Out of the Shroud Hole

As you have found out Air Flow is one of the Keys to keeping the Engine running cooler

Another Key is a Rad with as few Rows of Tubes as possible
and if there are other things in Front of it like a A/C Condenser the ability to Pull Air thru them

My Small 2 Row 1.25" Wide Tubes Alum Rad Core that is only 23.5" Wide X 16" High
with SPAL Dual 11" Efans/Shroud keeps my BBC Temp at 180* to 190* in City Traffic
when Both Efans are on in HOT 30+C Temperatures and with a Trans Cooler in Front of the Rad







You did it right with the proper electrical fan setup IMO. I would LOVE to go elec fans but the radiator I have now is not what I want long term, plus there is a bend in the rad support that would have to be addressed first.

I have a very small cooler for power steering that's more behind the bumper than the grill. That wouldn't affect anything.

You may be right, and I am thinking the same thing, that a different fan may be all I need. A lot of people like the thermal clutch fans, which I'd be tempted to try. I know very very few people suggest flex fans.
 

·
Registered
Joined
·
1,768 Posts
I’ve got a ‘72, with a factory fan clutch, fan and fan shroud. I’m currently running a single core (1.25” tube core) aluminum radiator with plastic tanks (Murray 433322) to cool a stout big block.

It will sit and idle all day long on a 90* day at 180-185*.

It has a *ton* of airflow at idle (and all other times.) I made sure the shroud was sealed tight to the core so all air flows through, not around.

From what you describe, a different fan and maybe checking the shroud is sealed well may just do the trick as your problem definitely sounds like an airflow problem.
 
  • Like
Reactions: p40

·
Registered
Joined
·
1,041 Posts
I keep seeing more and more of engine overheating issues on the forum, kind of wondering if its just common mistakes or if something is changing with fuel quality? Just a thought. I can say it's darn hot here in south Louisiana (about 95f today) and I had a small block idling for a good while today trouble shooting ac issues, never got over 185, I am running a 185 t stat and have the dual windstar fans, it's cooling the engine but I don't think it's enough for the ac though. I know this ain't much help but just putting it out there.
 

·
Registered
Joined
·
4,975 Posts
I’ve got a ‘72, with a factory fan clutch, fan and fan shroud. I’m currently running a single core (1.25” tube core) aluminum radiator with plastic tanks (Murray 433322) to cool a stout big block.

It will sit and idle all day long on a 90* day at 180-185*.

It has a *ton* of airflow at idle (and all other times.) I made sure the shroud was sealed tight to the core so all air flows through, not around.

From what you describe, a different fan and maybe checking the shroud is sealed well may just do the trick as your problem definitely sounds like an airflow problem.
On my 67 Abody and 468BBC/T400, I run a similar setup. An APDI/PRO 8010322 Radiator - single row, aluminum 1 1/4 core with plastic tanks + Flex-a-lite 1818 fan, and no shroud. Temps at extended idling on a 100* day may creep to 205 with a 180* thermo and stock water pump. Cruising at 20mph or more temps are constant 185-190.
 
  • Like
Reactions: BillyGman

·
Premium Member
Joined
·
8,929 Posts
I have a 1970-468 Driver. It has factory A/C. The cooling system design is over FIFTY years old and it cools just fine. When all else fails, Just copy what the factory did, For the most part the factory stuff works.
I can park my 468 in the sun on a hot day, Leave it idle untill its out of fuel. I also have a one owner 454/M-22 car with factory A/C. I has not overheated in my 50 years and 5 months of ownership.
When I built my driver 468, I just made a carbon copy of the factory cooling system, WHY? Because it works.
A Mechanical or Electric cooling system will work just fine....." IF " it is designed for your car " AND " WILL move enough--"" Cu. Ft. of Air Per. MIN.""
KEEP IN MIND.... " Good parts aint cheap and Cheap parts aint good ".
Bob
 

·
Premium Member
Joined
·
8,512 Posts
You answered your own question when you said in your 1st post :
I have a 6 blade aluminum fan. Oddly it doesn't have any real contour in the fins.
I do NOT have any clutch on the fan, it's bolted to the water pump.

To me it sounds like you have an older worn out flex fan.The way flex fans work is at idle the curved blades chop and pull more air through the radiator because there is no airflow like from higher road speeds.Then when your engine is turning 1500-3500 RPM the blades flatten out and don't draw as much air through the radiator because you already have the airflowing with the car's speed. Also theoretically, it takes less HP to spin them with the blades flattened at higher RPM's.
Your engine cools great at speed because of the airflow at those speeds.I think a new flex fan would solve your heat problem at idle.
 

·
Registered
Joined
·
5,590 Posts
You did it right with the proper electrical fan setup IMO. I would LOVE to go elec fans but the radiator I have now is not what I want long term, plus there is a bend in the rad support that would have to be addressed first.

I have a very small cooler for power steering that's more behind the bumper than the grill. That wouldn't affect anything.

You may be right, and I am thinking the same thing, that a different fan may be all I need. A lot of people like the thermal clutch fans, which I'd be tempted to try. I know very very few people suggest flex fans.
As long as you have Room for the Clutch in Front of the new Fan with Curved Blades
 

·
Registered
Joined
·
104 Posts
More of a rant, but very very open to suggestions.

I joined a car cruise on tuesday, and while it was hot for local weather, it was only around 24-25C (75-77F) and my car just cannot creep at idle. It got up to 240F (sensor in the manifold) before I had to bail out. The crazy part is I put the car on the highway and at 100 kph (62 mph) I got down to 164F coolant temps. 76F temp climb, I could probably do just as well without a fan.

I have a 6 blade aluminum fan. Oddly it doesn't have any real contour in the fins.
I do NOT have any clutch on the fan, it's bolted to the water pump.
Aluminum radiator, no idea the core count or brand.
Factory GM shroud. - the fan could be brought in closer to the block I suppose, as right now the fan is about flush with rear of the shroud.
Timing is at 18 initial, doesn't make a diff if i change it to 22 or so.
AFR is at 13.75, doesn't matter if I make it richer or leaner.
I have 2 temp sensors, so not a faulty sensor.
Weiand aluminum water pump


When driving and there is airflow, it's clear it will cool sufficiently. It seems there is just no airflow at idle while sitting still.

I think I need to get a different fan arrangement, or could it be possible there is something messed up in the water pump that is preventing it from keeping the coolant flowing at idle RPM?

What the fan does (regardless how it is 'powered') is create a pressure differential (lower on the engine side of the radiator). Air flows from the 'bumper' (high pressure side) side, thru the radiator (to the low pressure side), and exchanges heat from the coolant to the air. The more air flow required, the greater the pressure differential.

For the OEM style 'mechanical' systems, that 'creation' of the pressure differential is provided by the belt driven fan (needed at 'idle', and very low vehicle speed). The shroud on an OEM 'mechanical' system increases the pressure differential. At vehicle forward speed (25-30 mph), the pressure differential is 'free' (naturally provided from the air speed 'pushing' at the front of the radiator; w/o the need of a fan). Restrictions at the radiator reduce the pressure differential, and the air flowing thru the radiator. The fan clutch does not enhance cooling. It allows for the torque used to turn the fan to be used for another purpose (propulsion for example).

Electric fans (and their 'shrouds) tend to have significant more air flow restriction. So, they need to be 'sized' to do the entire job; at idle, and at speed. AND, be 'matched' to a radiator design that compliments the air flow provided. Also, those 'amps' don't come free. It takes additional torque to turn the alternator to provide them.

My point is there is no right or wrong type of system.

Because I don't want to design an electrical system, I would rely on the GM design and 'tweak' it; if a modified engine required 'additional' cooling.

Not enough 'cooling' at idle? Modify fan 'system' (examples; add shroud, more pitch on blades, more blades, nix clutch). The goal is to increase the pressure differential.

Not enough 'cooling' at forward speed? Focus on radiator. Larger surface area for more air flow. 'Internals' designed to keep coolant in the radiator longer. Eliminate restrictions at much as possible.

Just my opinions.

Pete
 

·
Registered
Joined
·
256 Posts
I'll just add that I wouldn't run a flex fan if you gave me one, the fan really needs to be spaced properly in the shroud, and make sure that nobody has swapped pulleys and screwed with the water pump speeds. Next, make sure the radiator isn't packed with crud, make sure your cap is good, and make sure your coolant mix ratio isn't too high. I am also of the school of do what the factory did and then adjust only as absolutely necessary. Due to a change of plans, I have a four row big block radiator in front of a mild small block, clutch fan and stock shroud. That system holds just short of five gallons on coolant and I don't think it would overheat if I drove through a blast furnace.......
 

·
Premium Member
Joined
·
4,110 Posts
I started 20 years ago with a flex fan on a zz4 350, which I swapped out a week or two later with a factory BB clutch fan/shroud setup (with spacer), stock 3 core HD radiator. It ran right at 180. I swapped in some Windstar electric fans, and they worked, but it ran 10-15 degrees hotter, so I went back to the clutch fan. Now it's got a 454 in it, with the same BB fan and shroud, and it still can idle all day in 90 degree weather at 180. It's simple, reliable, and flat out works. I should add I have a trans cooler too. I don't have the load on the electrical system, and no relays, wiring, connectors, or fan motors to worry about. All my parts were new stock replacement stuff.
 

·
Premium Member
Joined
·
1,135 Posts
I'll probably get flamed for this as a lot of guys hate flex fans..... but I would try one of these:

https://www.summitracing.com/parts/der-17018

The one above is an 18" clockwise rotation. Very well made and engineered to pull a lot of air at low speeds. This fan placed correctly in a good fitting shroud should do the trick.

Electric fans have their place but it's very expensive to switch over. I would think for around $100-$150 you could do the fan and shroud.

I have one of these on my 67 (which has a smaller core area than yours) and it will keep my 502 cool in 90 degree weather of the midwest.

In addition I used adhesive weather stripping to make sure the radiator was sealed 100% to the core support and the shroud was 100% sealed to the radiator. As someone else said pressure differential is how the air flows through the rad.
 

·
Registered
Joined
·
6,367 Posts
Discussion Starter #15
Can you post a photo of your set up - as it relates to the fan and shroud. Normally you want the fan half in - half out of the fan. Also what is your pulley system look like - photo there too.
I'll snap a pic a bit later, but the fan is about flush with the shroud. It could be pulled in by about an inch I'd say.

I do have aluminum pulleys, but I don't think they are underdrive. I
 

·
Registered
Joined
·
6,367 Posts
Discussion Starter #16
I'll just add that I wouldn't run a flex fan if you gave me one, the fan really needs to be spaced properly in the shroud, and make sure that nobody has swapped pulleys and screwed with the water pump speeds. Next, make sure the radiator isn't packed with crud, make sure your cap is good, and make sure your coolant mix ratio isn't too high. I am also of the school of do what the factory did and then adjust only as absolutely necessary. Due to a change of plans, I have a four row big block radiator in front of a mild small block, clutch fan and stock shroud. That system holds just short of five gallons on coolant and I don't think it would overheat if I drove through a blast furnace.......
Cap seems fine. Have cleaned the radiator, plus I am sure it's not clogged otherwise it'd run hot while moving too. I run like 25-33% coolant, the rest distilled water.
 

·
Registered
Joined
·
6,367 Posts
Discussion Starter #17
I'll probably get flamed for this as a lot of guys hate flex fans..... but I would try one of these:

https://www.summitracing.com/parts/der-17018

The one above is an 18" clockwise rotation. Very well made and engineered to pull a lot of air at low speeds. This fan placed correctly in a good fitting shroud should do the trick.

Electric fans have their place but it's very expensive to switch over. I would think for around $100-$150 you could do the fan and shroud.

I have one of these on my 67 (which has a smaller core area than yours) and it will keep my 502 cool in 90 degree weather of the midwest.

In addition I used adhesive weather stripping to make sure the radiator was sealed 100% to the core support and the shroud was 100% sealed to the radiator. As someone else said pressure differential is how the air flows through the rad.
That was going to be the next question. If I get a thermal clutch, which fan do I go with. I think it's quite clear my current fan does not pull enough air. I do plan on getting some weather stripping to seal the shroud, but I don't think that's the route of my problems.

I absolutely do NOT want a big heavy steal fan. Anything below 2000 rpm I am quite sure even a flex fan will maintain shape and pull enough air as long as it's big enough and has a good pitch/shape.

so what do you guys recommend for fans
 

·
Registered
Joined
·
3,055 Posts
To each his own...

Put me in with the clutch fan people...

I remember going through the junk yards looking for those big GM Luxo-bombs for those clutch fans... They used to be such a sought after part! We would remove the bi metal and rotate the shaft to the next lower position so it would take less horsepower off the engine. They were set up to cool a big 455 with AC in an overly crowded engine compartment, my 421,427 or 454 didn't need this kind of cfm..
 

·
Premium Member
Joined
·
1,135 Posts
You have mine.

A lot of guys on here are big fans of clutch fans and they do pull gobs of air at low speeds. I myself always question how fully locked up the clutch was a various loads/speeds. Many years ago we had a gentlemen who was a design engineer for an aftermarket cooling products vendor who helped with recommendations, his name was Steve Jacks (HOTRODSRJ). He had done a lot of research and thought the Derale fan was as good if not better than the factory clutch fan.
 
  • Like
Reactions: hydro462

·
Registered
Joined
·
256 Posts
You have mine.

A lot of guys on here are big fans of clutch fans and they do pull gobs of air at low speeds. I myself always question how fully locked up the clutch was a various loads/speeds. Many years ago we had a gentlemen who was a design engineer for an aftermarket cooling products vendor who helped with recommendations, his name was Steve Jacks (HOTRODSRJ). He had done a lot of research and thought the Derale fan was as good if not better than the factory clutch fan.

Not trying to be a jerk, but if you helped design aftermarket products, would YOU admit it if they weren't as good as OEM? I just know that 95% of the time, the factory fans work fine, and I know several people that have created more problems than they solved be running aftermarket fans or using electrics when they really weren't needed. I think we have ALL been guilty at one time or another of over thinking stuff....
 
1 - 20 of 152 Posts
Top