Clearance between fan and radiator - Team Camaro Tech
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post #1 of 16 (permalink) Old Apr 8th, 01, 12:22 AM Thread Starter
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Joe
 
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I need some help again.

I just got my new radiator from Rick's - 4 core BB with auto trans. Looks good, mounted perfectly. Got a new GM 7 blade fan and thermo clutch as well.

When I went to mount the fan, there wasn't enough clearance between the radiator and pump to get the fan on! I couldn't get past the end of the waterpump shaft. Needed about 1/4".

I took the radiator back out and bent the supports inward to make a slight "s" to give
me the clearance I needed. I also filed down the "nubs" that hold the thermo spring a bit.

I could now just barely get the fan on. Noe that it is mounted there is just enough clearance to get the belts between the fan and radiator (scraped a bit, but still goes on).

I have just under 1/2" between the fan and radiator. The fan blades are centered in the shroud like it shows in the assembly manual.

Is this normal? Seems a bit close. I know the engine isn't going to move forward or the radiator backward, but it seems really close to me.

Anyone out there have a stock BB radiator/clutch fan setup? What is the clearance?

Thanks again!

Joe

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[This message has been edited by Joe G (edited 04-08-2001).]
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post #2 of 16 (permalink) Old Apr 8th, 01, 01:28 PM Thread Starter
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Anyone?

Thanks, guys
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post #3 of 16 (permalink) Old Apr 8th, 01, 03:22 PM
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for best cooling a fan need's to be about 2" to 5" from the radiator. and you need a shroud! they will make the fan more efenctant.
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post #4 of 16 (permalink) Old Apr 8th, 01, 04:28 PM
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It's been my experence that the fan should almost fit all the way into the shroud. Maybe 3/8" to 1/2" of the fan should be out of the shroud. I don't think the distance from the core is an issue other than having enough room to get belts on or in the unforseen bad bearing in the waterpump causing the fan to wobble.. Look at how close the electric fans are to the core. How close should not impact the draw...

How much thicker is your 4 core over the old radiator? What size water pump are you running? It might be some work to switch to the short pump (pully ailgnment etc.) if you have the long now, but might by you some room.

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post #5 of 16 (permalink) Old Apr 8th, 01, 06:42 PM
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the distance from the core to the fan is very important. most electric fan's are too close, i am talking after market fan's. the OEM electric fan's are normaly about 1" to 2" from the core because of the shroud they are mounted too.

you need distance from the core so as to not stall the fan. most fan's, electric or motor driven, can pull more air than can flow throught the radiator core. the distance from the core help's to keep the fan from stalling, as in displaceing so much air that the blade's do not bite as well.

DJD you aqre right about aprox. half the blade of a motor driven fan beeing covered by the shroud. also you need about 1/2 to 1 inch clearance around the fan, this is to help creat a better flow and so the air at hi speed has a place to go beside's through the fan.
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post #6 of 16 (permalink) Old Apr 8th, 01, 11:19 PM Thread Starter
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Thanks, guys.
The fan blades are half in / out of the shroud so that's correct.
There is ~1 inch clearance around the shroud.

Stock shroud, stock 7 blade fan, clutch and stock long shaft water pump.
Stock radiator support; radiator is tight against the support (now).

4 core radiator is 2 3/4" thick. Old 3 core ~ 2 1/8". Old fan was a flex fan with spacer so really not a valid comparison.

1 1/2 inch clearance from fan blade to radiator.
These all seem correct.

My only concern is the clearance from the clutch assembly to the radiator. I have less than 1/2 inch from the center tip (thermo spring) to the radiator. Everything else seems OK.
Am I nuts? It just seems a bit tight. As I said I could barely get a belt between the tip of the clutch and the radiator.
But it did fit! Besides, there isn't much I can do about it without relocating the radiator support or something.

Thanks again. I sure appreciate the help and conversaton.
Joe

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post #7 of 16 (permalink) Old Apr 9th, 01, 08:53 AM
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Joe,
From what I have learned from others through the years, that is a bit close for my comfort. I go by the 'rules' that say the fan should be 3/4" to 1" from the radiator. This will allow for any blade flexing, or motor movement while still getting good air pull through the radiator. With this setup, I have been told you don't need a shroud and this is how GM did some of the eary cars. I have not tried it both ways, so don't really have an opinion on that. If the fan sits more than 1" away from the radiator, then you need a shroud and need the clearances mentioned already around the shroud. One other thing if running a shroud, I go by the 'rule' that for optimum flow, approx. 1" of the rear of the blades should stick out from under the shroud. I have usually used this method with lots of success. Then again, I have never had a car were I thought the fan was too close to the radiator either.

Good luck, hope that helps.

Bill C.


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post #8 of 16 (permalink) Old Apr 9th, 01, 09:10 AM
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Is it possible you have the wrong clutch. It would seem likely that there could be different length shafts on these clutches for various applications. Maybe Ricks sent you the wrong one. Just fishing.

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post #9 of 16 (permalink) Old Apr 9th, 01, 09:23 AM
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That is too close I speak from experence. I stuck one in the radiator of my car when I slamed on the brakes. Not a good thing to do.

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post #10 of 16 (permalink) Old Apr 9th, 01, 09:40 AM Thread Starter
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Very possible that the cltuch may be too long. The box listed it as 67-69 BB clutch, but.....who knows.
I thought all the BB clutches were the same, but I measure the one for my 454 truck and the truck one is about 1/2 longer than this one.
I think I'll check my local auto store and make some measurements. If I can find a shorter one, I'll get it. I would think that as long as it's for a GM BB, it would work OK as far as temperature, etc. Glad I haven't added the antifreeeze yet!

Oger, I guess you must have hit the brakes pretty hard to make the engine move forward!!
I want your brakes!

Thanks again.

Joe

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post #11 of 16 (permalink) Old Apr 9th, 01, 07:02 PM Thread Starter
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Well the clutch is correct too.
I removed the radiator and modified the brackets to get it flush with the radiator support. Put some rubber where it touches to keep from rubbing a hole it it.
Now I have about 3/4' from the radiator to the clutch tip.

Everything is happy now.

Don't know if I just got a bad fitting radiator or my car is different, but it is in and fits now!

Thanks for the help.

Joe

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post #12 of 16 (permalink) Old Apr 10th, 01, 10:29 PM Thread Starter
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Cool

Back again with a question. Now that it's all installed, I'm still worrying.

The shroud is a GM Big block shroud. Now that I have moved the radiator forward enough to clear the clutch, only about 1 inch of the fan blades are in the shroud. The shroud is pretty shallow. The shroud /fan relationhip is probably OK but is not what I would think is correct. Most of the fan is outside the shroud.


I'm still wondering how the factory BB radiators and fans fit. Maybe this radiator is too thick at 2 3/4"? I wouldn't think so, but don't know what else to think.

I have the radiator pressed forward enough that the tanks almost rub on the suppport.
I had to "adjust the mounts to center the radiator tanks over the opening in the body support. The tanks just barely cleared each edge.

I'm thinking maybe the brackets on the radiator were just too long and moved the radiator too far toward the engine.

Anyway, it's in with the "adjusted" brackets so I couldn't send it back anyway.

Sorry for the long winded posting but wanted to be as accurate as possible.

Any factory installations out there?

Thanks again

Joe

------------------
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post #13 of 16 (permalink) Old Apr 11th, 01, 06:07 AM
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Joe,

How much, on a percentage basis, does the fan go into the shroud?

As noted above 1/2 - 3/4 of the fan should be in the shroud.

Don't be surprised if the radiator is not correct. Many of the restoration houses get them from U.S. Radiator here in Los Angeles. I bought mine direct from USR but it did not fit. The bracketry was not even close. I took it back and they looked at me like I was nuts. The shop manager got involved and he hauled out the core support they used as a template. The radiator did not fit their core support. And guess what? Sitting on the shipping dock, which is next to the counter, are two pallets stacked six feet high with radiators with a big D&R address label. They had to rework all of them. Can you imagine how many incorrect radiators were sold? UGH!

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post #14 of 16 (permalink) Old Apr 11th, 01, 07:03 AM
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Joe don't worry about it there hasn't been any sunshine in Benicia for over 20 years. Did you ever get the converter sorted out I am curious if Jimmy was right about the hub being cracked.

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post #15 of 16 (permalink) Old Apr 11th, 01, 08:57 AM Thread Starter
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Thanks Carl. The radiator is built by US Radiator, sold by Rick's (and others). I picked for that reason. I had thought they had a pretty good reputation.

The radiator looked good, mounted perfectly (so I thought). It was just too close to the fan clutch.
The fan blades are almost 1/2 way in the shroud on the bottom and 1/4 inside on the top.
I had drilled another hole on the shroud to pull it closer to the radiator on top. After I moved the radiator closer to the support, there was ~3/8" gap on top. The radiator is also 1/2" closer to the pass side to center it in the support opening to get it flush. This twisted the shroud a bit using the stock hole. Didn't like the look of that.

Now that I've measured top and bottom, I guess I pulled the top of the shroud in too close. I can move it back a bit and live with the gap if that will make the fan work better.

My "adjustment" is probably not mounting the radiator perfectly parallel with the support either. Looks even tho'.

Didn't think this would such a pain! Replacement radiators should be just that!
At least it will be running soon!

I also mounted the external tranny cooler on brackets in front of the radiator rather than use the ties through the new core. Don't know how thick the tubes really are and didn't want to risk wearing a hole in one.

Thanks again. This is a great place!

Joe


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