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Join Date: Mar 2005
Location: Jeannette Pa. near pittsburgh
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.
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1970 SS LS-5/M-22 El Camino- Org. Owner-AACA 2016-Senior Grand National Winner---MCACN-GOLD-2013
1970 ( FRAUD) SS 468 Station Wagon - Driver.