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Old 07-09-2017, 01:18 PM   #1
Lee B.
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Fan shroud for '65 4x4 Big Block

I've got a '65 Chevy 4x4 truck I put big block in about 20 yrs ago. Set it up originally with 3 electric fans in a shroud. I've always had running hot issues with it during Phoenix summers. Temps would go over 230 deg and I would shut it off, leaving the fans on. I've done everything possible to correct it : Ron Davis direct fit aluminum radiator (2- 1" rows), heavy duty hoses, changed timing, carb tune, t-stats, coolant ratios... The best I've ever had it was after reducing the crank pulley to 1:1 from the overdrive pulley that's stock on the 454 ci motors of the late '70s and '80s. As I was mostly having trouble at rpms 2500 and up, no matter the speed this seemed the way to go and helped, at least it didn't go over 220 deg. It was recommended I try a performance water pump. This again made it go over 230 deg. (pushing coolant too fast?). I've gone back to a stock water pump and am trying a 19-1/2" clutch fan with heavy duty clutch. Now it runs at any rpm and any speed staying around 210 deg. but gets hot in stop and go traffic. I haven't yet put a shroud on it but I think I'll have to build one. The only one I can find on the internet is for a small block and I hate to spend $150 for a plastic piece just to look at it.
Does anyone have a suggestion for me?
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Old 07-09-2017, 10:35 PM   #2
'63GENIII
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Re: Fan shroud for '65 4x4 Big Block

Hey Lee, I used a stock reproduction for mine. I also used the serpentine off of a '97 454, along with the stock water pump and giant steel 7 blade fan (could be 19")with a heavy duty clutch. I used this set up for the old carbureted 396 and for the current FI 454.

The replacement shroud took a little trimming all the way around and a little more on the bottom. On the hottest of days around (109 on Altamont a couple weekends ago) here it will cap off at 215 while towing 6 or 7k lbs. Never any higher and it will come right back down to 190 when at speed. I have a 180 thermostat and original 4 core brass radiator. The clutch locks up when cold for a few minutes and then when needed as it gets hot (above 200 deg).

It never gives any indication of overheating although I wish I could get it down to 160 - 170 deg so the computer is less likely to pull timing.

It does sound like there might not be enough airflow which a shroud should help with. I know it did on mine.
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Old 07-10-2017, 10:29 PM   #3
64shortbox
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Re: Fan shroud for '65 4x4 Big Block

I saw this a few years ago. This guy built his own fan shroud out of fiberglass & cloth. I was thinking about doing this until I went with a Lincoln Mark VIII electric fan.

http://www.route66hotrodhigh.com/FanShroud.html
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Old 07-10-2017, 11:15 PM   #4
Lee B.
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Re: Fan shroud for '65 4x4 Big Block

Thanks for that Chris. I thought that might work with the repro but I didn't want to drop $150 bucks and then start whittling on it. I decided to use the picture of that shroud and copy it with sheet metal. I also saw the guy that built the one from fiberglass. It looked perfect, but too much work for me. I don't know any thing about fiberglass. Metal I understand, I'm just lazy and hoped I could buy one that would fit right out of the box. Chris, that's the same fan and clutch I'm using but I've got the old '79 vintage pulley and belt system. I'll post some pics when I get it done.
Lee
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Old 07-11-2017, 09:22 AM   #5
Brad54
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Re: Fan shroud for '65 4x4 Big Block

Mine is a small block, but I live in Atlanta.
I had that same clutch and can on mine, no shroud, and a 4-row reproduction radiator.
It kept cool in Atlanta traffic in the summer.
Two things I "cheated" with were using a 3/4 ton radiator instead of the half ton: its a couple inches wider, and a few inches taller, yet bolts into the 1/2-ton core support using the stock mounting holes.
I also put a 160-degree thermostats in it in the summer: it opens sooner and maintains a lower operating temperature, and therefore gives me some extra time when it starts climbing in stopped traffic. If it's operating at 180-degrees, then it's already at 180 when I'm stuck and stopped.
I've also found Water Wetter to be a big help on vintage cars.
It's not snake oil. I did a big magazine article on cooling systems several years ago and got into the science of water wetter and other surfactants. They work, and aren't a bandaid.
Electric "Pull" fans behind the radiator are also better than electric "push" fans in front of the radiator. But big 7-blade clutch fans are my favorite.
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Old 07-14-2017, 12:28 AM   #6
Lee B.
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Re: Fan shroud for '65 4x4 Big Block

Thanks everyone for all the good info. I knew I'd find help here.
Lee
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