size of fan to use for 71-72bbc shroud - Chevelle Tech
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post #1 of 6 (permalink) Old Jan 1st, 14, 10:13 PM Thread Starter
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Vince
 
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size of fan to use for 71-72bbc shroud

i've purchased a 71-72 bbc style fan shroud to get more air pulled thru my rad-assy.
currently using a 69-70 bbc style fan shroud with a large blade flex fan.
don't want to run a factory fan and thermo clutch, don't care about the fan noise
which 19'' fan should i run for max airflow

i'm looking at a couple of 19"diameter units, 4-blade and 6-blade unit.
4-blade is 3.5#
6-blade is 5#
both about same price,
which should give better airflow the 4 or 6-blade unit???

68-Malibu 427bbc/t4oo/3.73-12bolt/pro charger f1-r

Last edited by VinceS427bb; Jan 2nd, 14 at 1:54 AM.
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post #2 of 6 (permalink) Old Jan 1st, 14, 11:04 PM
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Mark
 
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Re: size of fan to use for 71-72bbc shroud

Summit offers a Flex style fan for RV use , no noise . A friend is using one on his 66 with a 540 . Hes had it 6 years and I don't have a part number . You'll have to call the them like he did. Myself I like the 2747 Hayden clutch with the same fan you bought ,I've had no trouble with it not pulling enough air .
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post #3 of 6 (permalink) Old Jan 1st, 14, 11:08 PM
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Mark
 
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Re: size of fan to use for 71-72bbc shroud

Excuse me I thought you had a bought a stock fan . Good Luck keeping it cool .
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post #4 of 6 (permalink) Old Jan 1st, 14, 11:52 PM
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Re: size of fan to use for 71-72bbc shroud

Flex fans are junk. The blades on them spread out the higher the RPM pulling less air through. Plus they are more prone to coming apart when the rivets in them start rusting.
You are really better off with a stock 71-72 19" fan and a good HD clutch. FYI, some of the fan clutches are adjustable so they engage at lower temps to pull more air through the radiator.

Tom Rightler, MCC VP & Newsletter Editor

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post #5 of 6 (permalink) Old Jan 4th, 14, 2:13 PM
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Bob
 
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Re: size of fan to use for 71-72bbc shroud

As Tom Said.... Find a Dumpster, That is a good spot for a flex fan.
WHY? Lets go back to the 60s & 70s... FACT: ALL Big Block, G.M. Chyrsler, Ford. High Hp. engines had Clutch Fans, WHY? When the engine is operating in a slow or STATIC position, The heat exchanger NEEDS large volumes of air passing over the tubes to remove heat from the coolant.
When a High Hp. engine is moving at more than 35 M.P.H. at a constant speed, NO fan blade or clutch is needed, WHY? At this speed the Ambent Air is forced through the heat exchanger.
Also the Big Three auto makers DID NOT want a fan blade spinning at 6000 R.P.Ms. WHY? The force applied to the fan structure and whatever it is attached too. Would exceed the mechanical structure of " The blade,,Water pump and Fasteners.
FACT: Clutch fans never exceed the 3-4000 R.P.M. range. FACT: In the late 60s the Chrysler engineers, using dyno. testing and road testing for 13 months proved beyond any doubt, The fan blade with a clutch will keep the Mopar engines cool, Also provide a 16 H.P. net gain over any other design.
FACT: My 2010 6.2 half ton Silverado FWD has electric fans. The front of the Silverado heat exchanger is using tunneled outside air. ( A CAD Design ) You can only see the rear of the heat exchanger. The new airflow designs for cooling can not be incorporated into the 40-50 year old cooling design.
Cooling is all about AIRFLOW & Air Pressure It is not about ,,Who has the biggest heat exchanger. At this time I am to kool, It about 10-12 above Zero at my house.
Bob


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post #6 of 6 (permalink) Old Jan 11th, 14, 4:58 PM
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Re: size of fan to use for 71-72bbc shroud

Ground Up lists 3 for 71 up cars.

http://www.ss396.com/mm5/merchant.mvc?

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