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Fan to Shroud Clearance
Posted by: wittsend ()
Date: July 28, 2022 01:48PM

I searched this one prior to asking but the takeaway was:

1. There is no specific gap set by GM other than getting the fan hub height correct when changing the bearing.

2. 3/16" (.188) was an "acceptable" gap in one of the posts.

3. Within reason the tighter the clearance the better with 1/8"(.125) recommended.

4. As the fan becomes elevated..., so does the pulley and that can cause belt alignment issues.

I set the bearing height on my '61 80HP engine to the 4.475 height stated in the June 2017 article of the Tucson Corvair Association. The article stated this number was an updated revision for 1962. TCA Article .

As I'm now installing everything I'm getting .260 clearance between the fan and shroud. At the tightest point a 1/4" (.250) drill will pass through but a 17/64" (.265) won't. So, I'm twice as low of the ideal 1/8" (.125) and 1/16" (.063) too low of what I have read to be 3/16" (.188) "acceptable."

I ask myself where did this go wrong??? I'm not the type of person to hammer the bearing in, look at it with one eye and mumble, "good enough." I spent HOURS on the internet gathering information. I precisely made a rod to 4.475 to set the height. I read the Tucson Corvair Association article and it said the 4.475 height is a revision over the 4.520-4.530 of my '61 manual so it seemed the right path to follow. The article was only 4 years old when I set my bearing. But right now I'm looking at that .050-ish difference and wanting it back.

Well, off to attempt to make a shim. Not sure .100 will still Keep the fan and pulley centered on the hub.

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Fan to Shroud Clearance
Posted by: wittsend ()
Date: July 28, 2022 02:04PM

BTW, the fan is a Mag fan. Not the steel fan the car supposedly came with.

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***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Fan to Shroud Clearance
Posted by: Timothy Shortle ()
Date: July 28, 2022 02:49PM

My opinion (you did ask for that, right?) is if using a 64 style fan, check the 64 manual. Same if using a 65 style. But I think what is most important is having a place for the air to go and not be restricted. In other words, have all the fins real clean and clear (deflashed) and have all the engine shrouds in place. Especially the ones below the cylinders. I also like to close the right upper fresh air duct. I suspect you did nothing wrong. This is all just my opinion.

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Re: Fan to Shroud Clearance
Posted by: wittsend ()
Date: July 28, 2022 05:20PM

Timothy Shortle Wrote:
-------------------------------------------------------
My opinion (you did ask for that, right?) is if using a 64 style fan, check the 64 manual.

The Mag fan came with the car. I would read about swapping out the steel fan for the Mag one but never recall that there were other considerations. But you may very well be right that there is a height difference on an EM going from a steel to a Mag fan.

In other words, have all the fins real clean and clear (deflashed) and have all the engine shrouds in place.

Done.

Especially the ones below the cylinders.

They are there.

I also like to close the right upper fresh air duct.

Done.

I suspect you did nothing wrong. This is all just my opinion.

Thanks. It just gets frustrating when you spend the time to avoid having problems..., and they still show up. sad smiley

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Fan to Shroud Clearance
Posted by: 63turbo ()
Date: July 29, 2022 09:55AM

wittsend Wrote:
-------------------------------------------------------
> I searched this one prior to asking but the takeaway was:
>
> 1. There is no specific gap set by GM other than getting the fan hub height correct when changing the bearing.
>
> 2. 3/16" (.188) was an "acceptable" gap in one of the posts.
>
> 3. Within reason the tighter the clearance the better with 1/8"(.125) recommended.
>
> 4. As the fan becomes elevated..., so does the pulley and that can cause belt alignment issues.
>
> I set the bearing height on my '61 80HP engine to the 4.475 height stated in the June 2017 article of the Tucson Corvair Association. The article stated this number was an updated revision for 1962. TCA Article .
>
> As I'm now installing everything I'm getting .260 clearance between the fan and shroud. At the tightest point a 1/4" (.250) drill will pass through but a 17/64" (.265) won't. So, I'm twice as low of the ideal 1/8" (.125) and 1/16" (.063) too low of what I have read to be 3/16" (.188) "acceptable."
>
> I ask myself where did this go wrong??? I'm not the type of person to hammer the bearing in, look at it with one eye and mumble, "good enough." I spent HOURS on the internet gathering information. I precisely made a rod to 4.475 to set the height. I read the Tucson Corvair Association article and it said the 4.475 height is a revision over the 4.520-4.530 of my '61 manual so it seemed the right path to follow. The article was only 4 years old when I set my bearing. But right now I'm looking at that .050-ish difference and wanting it back.
>
> Well, off to attempt to make a shim. Not sure .100 will still Keep the fan and pulley centered on the hub.


Heres where you went wrong: When the bearing is set exactly to spec, it is supposed to produce a height of 6" from the top of the pulley to the top of the fan shroud next to one of the carburetors. This measurement is only to assure that the belt is dead on in line with the fan pulley. It is not an assurance that this spec will produce given fan gap, its just what people have MEASURED when the bearing was set to 4.475 +/- 1/16. Applying the bearing height tolerance to the fan gap would produce .26"-.187". For your stated goals of driving this car to shows, I would leave it alone... call it good, as you would never be loading the engine hard enough to stress the cooling.
Without doing something to change the height of the pulley to compensate for bearing height changes, a fan to shroud gap of .187 should be considered the minimum clearance, especially if not running a fan pulley belt guide.

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: Fan to Shroud Clearance
Posted by: wittsend ()
Date: July 29, 2022 04:19PM

Thank you Kevin for the explanation.

I took these measurements (below) of the pulley height. Hopefully it is close enough. I now have the fan gap slightly less than 3/16" (.188) as an 11/64 (.171) drill will pass through at the tightest point.

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Fan to Shroud Clearance
Posted by: joelsplace ()
Date: July 29, 2022 04:38PM

Has anyone ever made a selective spacer for the generator/alternator adapter?

Joel
Northlake, TX
5 Ultravans, 138 Corvairs and counting...

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Re: Fan to Shroud Clearance
Posted by: 63turbo ()
Date: July 29, 2022 05:04PM

That should work just fine!! Just for useless after the fact "trivia", now that you have the pulley in a good spot- It sure seems like the vertical alignment is way more sensitive to the pulley being too high, versus being way off low. On my car, years ago, I added a 1/16" spacer under the fan to tighten the clearance closer to 3/16" and it turned the thing into an instant belt tosser. I'm pretty sure it was a little too high to begin with and did not check anything to near the precision you have! All I know for sure is that there were always belt rub marks on the bottom sheave and none on the top one. Once I took the spacer back out it was all good again. Another car ended up with a fan to shroud clearance of 3/8" which is way off low, and never had a problem with belt tossing, no matter what!

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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