[Rugratman]

Easier to move the fan in?

I was thinking that my goat has a bit of " dead space " from the front of the car to the front of the radiator, I wonder that when the fan is running is it pulling air just thru the middle of the radiator, so losing a square footage of toatal air thru the radiator? Bigger fan in the shroud increases a more broad amount of air across the radiator?
I ran the engine for a year with no shroud, it was running 210 +/-. I then put the shroud back on, did not seal it, then the temp would vary more, but still would climb at idle. 200+
I then sealed up the shroud with that sticky foam tape for windows, and spaced the new 18 inch fan into the shroud. That was the fix.
The fan I used was #FLX-1818 in the summit book. If I remember it was a 2 inch spacer. Long nose 11 bolt pump.
I hope this helps someone, I never even look at the temp gauge anymore.

[Tonyc]

WELL GEORGE, I JUST GOT BACK FROM A ROAD TEST FOR ABOUT 10 MILES. TEMP. NEVER WENT OVER 200. ALL I DID WAS MOVE MY FAN BACK OUT FROM THE SHROUD ABOUT 3/4 OF AN INCH. TEMP OUTSIDE IS ABOUT 82 . HOPE THIS HELPS WITH YOUR EXPERIMENT. I GUESS AWAY FROM RAD . IS BETTER THEN CLOSE UP THANHS AGAIN FOR ALL YOUR HELP . TONYC

[GTOLou]

One of the best things I have done for cooling was to add a spacer and move my fan forward. Now, the back edge of the fan is equal to the housing. In other works the entire fan is just in the housing.

I don't have much objective proof it helps. It does run cooler on the gauge. The only objective proof is that the same shop towel that stuck to my grill poorly before the move, now sticks very well. I believe it helps direct more air flow through the radiator.

[Geoff]

Seems to be lots of variations in results. Some run cooler with the fan buried in the shroud, some run cooler when the fan is pull pulled out some, with many variable factors to distort the outcome. Many factory cars, different brands too, seem to vary. Which makes me think that whether the fan is 1/4 in, 1/4 out or anywhere in between is not critical, because if it was, every car would have it's fan located that way.

Rugratman looks like he got a big temp reduction, 30 deg, by moving his fan into the shroud. When I read his post again, I picked a couple of words I missed on the first read, "1/2 inch gap". The gap he formed from the tip of the fan blades to the shroud was 1/2". I made mention of this earlier in an earler post in this thread. I believe it is most important to keep this gap to a minimum to maximise shroud efficiency & I also believe this is what has given Rugratman his cooler temps, & not the in/out position of the fan.

[Rugratman]

Geoff, that could very well be. I replaced the fan and the spacer at the same time.
There is alot less air flying out the engine compartment though.
To be honest, once I got the temps down I haven't touched anything, I am afraid, I will jinx myself. I used to stress about the heat, with aluminum intake, aluminum heads......
At my club picnic years ago, Chuck Roberts who wrote our Resto book, looked into my engine and told me to use a big station wagon fan, as they are bigger and fill the shroud more. I couldnt find one at a junk yard, so I bought the flex fan.

[Batman]

well, the cardoard extension didn't work so well. It moved a bit and was difficult to position exactly on the fan. also, a clutch fan contacting cardboard slightly sounds like a combination of exhaust leak and a bad valve all rolled into one

I have come up with a better solution for the test and have my mechanical guages hooked up under hood. Maybe tomorrow.......

[Batman]

I will also be able to tighten the fan/shround clearance as well with the new setup, so I can test fan extension into the shroud as well as clearance from fan tip to shroud

[speedshopmike]

see similar but newer thread in this same forum.
good topic, george.
thanks
mike

[BMFH]

Hello All

I know that this is a VERY OLD THREAD, Hope this helps

I have been reading through your posts on cooling Problems for the Ol'e Pontiacs.

I have been a Vehicle Mechanic for 40 years and am also an old Helicopter Mechanic too, Viet Nam era on H-53 Helicopters.

If you look at almost any clutch fan you will notice that the blades are not evenly spaced, if you look at the Alternator Fan you will notice that they are also not evenly spaced.

The H-53 has 6 rotor blades, if they were all evenly spaced then the rotor would Stall, meaning that it would quit moving air through the rotor disc, then you would experience the sinking feeling of settling with power, Not Good. The rotor blades move fore and aft as they rotate on the rotor head preventing the Stall Problem.

The reason that the fan blades are not evenly spaced is to disrupt the airflow through the fan Creating Turbulence in the air stream in an effort to prevent the fan air movement from stalling.

The reason that the fan is correctly installed with approx 1/2 of it outside the Shroud is because it becomes much more efficient in moving the air in two ways, one the blades can not Stall inside the Shroud because of the un-even blade spacing, and by being half the way out of the shroud the fan acts like a centrifugal compressor in that it can sling the air off the tips of the blades too thus greatly improving airflow.

I hope this helps with the understanding of the air flow somewhat.

Take Care

Dusty

[FrankieT/A]

Ok this an old thread that more than likely the people who contributed at the beginning of this thread probably will never even see this.... With that being said.....

The air off the tips of the fan and air off the rear of the blades is a bi-product.
Here's what's actually happening... In front of the fan blade there is a low pressure area. Indeed being created by Bernoulli's Principle. The air is not being sucked through the blade, it's being pushed.. When the low pressure is created in front of the fan, surrounding air rushes to the low pressure. This is how planes fly! They don't ride on the air they are sucked up to it. A propeller on a plane is nothing more than a rotary wing ( like a helicopter). Prop planes suck themselves through the air. Back to the radiator... When you have a well engineered fan shroud, the fan causes the low pressure, surrounding air rushes to right in front of the blade. But the shroud directs the air to mostly pass through the radiator. It is paramount that the shroud fit tightly so as the air has no choice but to pass the core area.
Moral of the story, don't concern yourself with how much air comes off the back of blades, instead be aware of how it's coming in the front.
This is why the blade needs to be half out and half in. We are working with suction (low pressure). Not blowing (high pressure).
Hope this helps!

[thebrat1967]

I had a flex fan that was completly out of the shroud I replaced it with the factory fan that was 1/2 in and out and no more overheating
Thanks I appreciated your post

[BMFH]

Hello All

Started pulling the Ole 455 apart for the rebuild, guess what?

When I pulled the water Pump off it had a cast impeller with "8" Impeller blades, the most I have seen before this was 6 Impeller blades on a Cast Impeller.

It was a replacement unit and fit close to the backing plate, probably moves allot of coolant throughout the cooling system too.

The Only markings on the pump housing is a "G" and "G28" no other markings.

Maybe some one can ID the manufacturer of the unit. It is not leaking so will probably reuse it when the engine goes back together again, that is unless I can find another one like it.

I went to 3 different parts stores, they could not match it up, I did look at a A1- Cardone unit (O'Riley), it had Stamped Impeller Blades, Not Cast ones, and had about .100" clearance between the Impeller and the backing plate without the gasket.

Looks like the bad pumps are still in the supply system.

Again I know that this a very old thread, just some added information as FYI

Take Care,

Dusty

[bsblguy]

Again I know this is an old thread. I'm sitting home with nothing to do, no projects right now, and read about heating problem at hwy speed. I had this problem on my Trans Am, runs warm at 70 mph, cool at city speed. What I found was my lower radiator hose was collapsing blocking water flow. Replaced hose with one that had a spring inside, problem solved. Just throwing that out there for anyone that may have heating problems at speed.

[Batman]

Last weekend between football games I found the roll of Home Depot sheet aluminum left over from this fan/shroud placement experiment in my GP trunk:
http://forums.maxperformanceinc.com/...d.php?t=489874

Hard to believe that was over 6 years ago.