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Dick Boneske · 08-08-2006, 08:31 AM

No one has mentioned running no shroud at all. It doesn't matter whether air flows radially off the blades or axially back toward the engine, as long as it pulls air though the radiator. An argument could be made that there is more flow through the radiator without the shroud blocking the edges of the cooling fins. This likely would be true when the car is moving and the fan is not the main factor in moving air.

My '64 GTO came from the factory without a shroud, never had problems with overheating. This was a factory heavy duty radiator with 3.90 gears. My wife's '64 GTO has no shroud with a 428 engine, Tripower, factory four- core radiator, and aluminum factory clutch fan. Never have a problem overheating.

Batman · 08-11-2006, 12:12 AM

Quote:

The clearance can't be too small because the engine shifts when a load is applied. Too small a clearance and the fan will contact the shroud. I've never measure the amount of movement, tho.

You're correct. My T/A displayed symptoms (shaker/hood contact and fan shaving the shroud) before I realized the stock type motor mount was cracked. After replacing the motor mounts I observed the no load engine movement (semi rotational) from below and it was substantial. There is also quite a bit of slop in the F-body core support/subframe installation that can address the fitment of the fan to shroud clearance in order to center the fan in the shroud. I don't notice the same issues on my GTO.

73ta · 08-12-2006, 05:31 PM

George, just work the outside of the shroud with a hammer to close the gap to about .020", oh that's the other post. Are you just trying to raise more cash for retirement or start another mega thread to crash PY's server?

george kujanski · 08-13-2006, 12:24 AM

73: you saw thru my stealthy attempt. I'll go back to my corner and cry...sniff.

George

Tonyc · 08-15-2006, 06:08 PM

i have a over heating problem on the highway run so hot i have to pull over and slow down to 40 mph to get it back to 190. i took a look at my fan it's 1 3/4 from the rad. but the edge of the fan is even with the edge of the shroud.
shoule i try to get a clutch with a shorter shaft, to bring the fan out 1/2 way into the shroud? cluch shaft is 1 1/4 long. do they make a shorter shaft one?
thanks tonyc

george kujanski · 08-15-2006, 06:37 PM

Tony: are you saying the fan is mostly out of the shroud, or mostly in the shroud?

George

LPete · 08-15-2006, 06:52 PM

"An ideal fan and shroud design would produce a flow that is a hybrid between axial flow and radial flow."

From a Seattle University project for a fan shroud redesign for Kenworth:

http://www.seattleu.edu/scieng/engpc...20Overview.htm

This sounds to me like they're suggesting the fan be only partway into the shroud. It's interesting reading.

Tonyc · 08-15-2006, 07:39 PM

GEORGE MY FAN IS MOSTLY IN THE SHROUD. INNER EDGE OF FAN IS EVEN WITH OUTTER EDGE OF SHROUD. TONYC

LPete · 08-15-2006, 07:49 PM

George, I'm realizing more and more that this isn't a ducted fan. It could be, if the shroud was deep enough to completely encase the fan blade, but generally they're not -- the place with the least clearance is at the back of the shroud, and they taper out pretty quickly going forward toward the radiator.

Think how badly any radial flow inside the shroud would disrupt the airflow -- it seems to me that it could actually pressurize the inside of the shroud and badly restrict flow.

george kujanski · 08-16-2006, 12:24 AM

Lpete: interesting project. I wonder what the results were/are. They say the most efficient flow is a hybrid, and the statement of the problem is that the majority of the flow now is radial with the blade about 1/3 in the simple shroud.

Tony: it would be very interesting to see how your cooling would be if you moved the fan such that the blade would be about halfway in the shroud.
I don't know if there is a shorter shaft clutch. You could try the Hayden website perhaps.

If you can't locate one, perhaps you can try a 7 blade, large blade flex fan. You can get spacers for those. Results of the experiment would be unscientific since the fan is being changed also, but your cooling problem may be improved, which is the actual goal.

George

LPete · 08-16-2006, 01:33 AM

George,

It looks to me like the original problem in the Seattle U project may have been that a poorly designed shroud didn't promote much, if any axial flow. I think the opposite may happen when the fan is too deep in a properly designed shroud -- there is very little radial flow, therefore less than optimum total flow.

I spent quite a bit of time looking on the 'net and there sure doesn't seem to be much relevant information. Someone has to know this stuff!

george kujanski · 08-16-2006, 11:30 AM

Yep, the research team makes the statement that the best efficiency is a hybrid flow but they don't specifically say why.

If TonyC can get an improvemnt by moving the fan out of the shroud somewhat, that would be good info.

A fan halfway into the shroud seems to work ok, I just wonder if there is an improvement that can be made.

mzbk2l has test data that supports the 1/2 theory, but I would still like to have a formal explanation.

george

Rugratman · 08-18-2006, 01:55 PM

My take...without all the fancy big words..I don't know any.
I run a 67 GTO with a stock shroud. I am now using a large flex fan with staggered blades. 18 " fan.
I used a spacer to move the blades in, my fan is at least 2/3 rds of the way into the shroud. I had remarkable results in doing this. My reasoning for this is it gives for sqaure inch/foot area of sucking the air thru the radiator. I found on my previous set up, 1/3 rd in like the factory set up, it sucked less air thru the radiator. My test, kleenex on the front side of the radiator. My thought of this came, as you are driving down the road, more air is forced thru the radiator from the car just going down the road, hence more airflow is better. Now, the amount of blades, pitch, size of paddles might have been a issue also. So the fan is important also.
My temps dropped from 210 and variable from sitting at a light to moving down the road it would drop to 180.
Proudly saying here....180 all the time, even in 100 degree heat this summer.
My set up was also tweaked with the gap in the plates, aluminum radiator, etc.
The fan, and the shroud, and the spacer are what did the fix for me. No sh*t.

I had the same temp swings with the aluminum radiator too.
I tried everything. This was my fix.
I have now maybe a 1/2 inch clearance on the sides of the fan tips ends to the shroud. Also when the engine is running, and the hood is up, the staggered blades are quiet, and I don't have all the air blowing up out of the enging compartment, maybe it does flow less air, but the amount flowing thru the radiator might be in all the right places.
I vote for the fan inside the shroud, as far in as you can, big blades.
The old chevy's and caddies had the fan 18" inside the shroud, they used to look like a drainage pipe cut short, they worked.
I am done....I mentioned this here before, I was blasted here for loonieness, so I let it go. Now I rarely step foot into this forum anymore.

kate`s67gto · 08-18-2006, 06:42 PM

George i have my fan 3/4 in shroud (cadillac 18" fan). this car runs at 175* in town and out on hiway. Last year it would run at 165*, why the 10* climb this year

. No change to mixture of water to antifreeze 50/50 , Same carb set up and using manifold vacum same gas Sunco 94 now that hurts big time .

I know I'll blame it on global warming yeah that is it ...

. If memory serves me right aren't Monte Carlo fans inside the shroud and a good 10 to 12 " away from rad ?? I"m talking 70 to 76 model years . ?????

Old Goat 67 · 08-18-2006, 06:43 PM

Hey Rugratman,
"If they think you're crazy and you're not, Clap your hands....."

Oh, that's a different song, sorry.

If it's fact, it's fact!!! Case closed!

Charles

kate`s67gto · 08-18-2006, 07:02 PM

Look at this :-----------------------------------

Batman · 08-19-2006, 12:49 AM

George-

I put a GTO shroud on my GP and with the fan completely out of the shroud and several inches beyond the shroud it ran at 210 degrees + at idle consistently. I used cardboard and duct tape (yeah it's trailer park) and extended the shroud to midway on the fan and it runs at 180-185. I am going to take pic's and try fan fully in and just barely outside the "shroud".

I know it 'aint scientific but how else would you do the test? I thought about cutting a trash can and using the cylinder to extend the shroud but didn't want the humiliation. I will redo the test and do all measurements on the same day to eliminate variables.

PS shameless plug follows: anybody got a 69 GP shroud? I need one real bad...........

george kujanski · 08-19-2006, 02:36 AM

Looking forward to your results, Batman.

George

Colin · 08-19-2006, 02:58 AM

Quote:

Originally Posted by Dick Boneske

No one has mentioned running no shroud at all. It doesn't matter whether air flows radially off the blades or axially back toward the engine, as long as it pulls air though the radiator. An argument could be made that there is more flow through the radiator without the shroud blocking the edges of the cooling fins. This likely would be true when the car is moving and the fan is not the main factor in moving air.

My '64 GTO came from the factory without a shroud, never had problems with overheating. This was a factory heavy duty radiator with 3.90 gears. My wife's '64 GTO has no shroud with a 428 engine, Tripower, factory four- core radiator, and aluminum factory clutch fan. Never have a problem overheating.

My Ventura doesnt have a shroud either........no cooling problems at all, never gets above 185-190......motor isnt stock either.

Old Goat 67 · 08-19-2006, 06:05 AM

Batman,
That's what's called "thinking outside of the box."
Or, is it "inside the box"?
Very good idea!
Charles

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