Not necessarily. It wasn’t designed for his fan shroud. Pitch could be different too. Always use stock. Thousands of hours of R&D
Denny Manner told me, when I was having issues with the Estate Wagon and cooling, to use the 5 bladed fan. Said it moved much more air. I took off the 7 bladed fan and put on the 5 bladed fan and my cooling issues went away. Take it for what it's worth.
72 has the larger 22" opening shroud so the 20" fan is correct for that shroud. Those larger fans also have greater pitch at 2.25 to 2.5". That GM fan is a stock application on certain cars so it has plenty of R&D. And ir certainly came stock on many GM cars.
Well now I'm confused. According to my '72 chassis manual a GS 455 with A/C has an 18" 7 blade fan. I have a '72 Lark with a 350 & A/C now transplanting a 455 & keeping the A/C. I have the 20" 5 blade fan as well as the bigger shroud. Which is the correct fan? I'm not so much worried about correctness as much as the best cooling. I would like to know for my piece of mind. Thanks, Kyle
I'm just posting what Denny told me. This was with my 1972 Estate Wagon if that makes a difference. He was absolute on his saying it HAD to be a 5 bladed fan. It is a 20" fan.
I have decided to change the blade from the 20"7 blade to the correct 20"5 blade. This would make it the correct blade that GM wants on the car.So if anyone has one let me know
Kyle, that is a misprint. It’s a carryover from 70. Go by the assembly manual. Part numbers show the 5 blade is correct. In 71-72the GS 455 used the same shroud as the big cars unlike 70.
1972 Service manual page 60-10 Air conditioned and heavy duty cars are equipped with an 18" 7 blade fan (350cu.in.) and20", 5 blade fan (455 cu.in.) driven by a torque and temperature sensitive clutch.
I’ve stripped several 71/72 big blocks and they all had the big 5 blade fan. 70 big car 455 used the same 5 blade fan. 70 GS 455 is the only 455 that used the 7 blade 18” which is the same as a 350 with AC. The documentation is there if you know where to look. Cars without AC or heavy duty cooling this info does not apply.
71 and 72 big blocks had 5 blade fans. An 18" 7 blade fan fits a 70 shroud which is smaller in diameter than the 71/72 shrouds.
Seems a 5 blade might move more air than a 7 blade . This has been discussed countless times. The staggering offset fan blades pull bigger gobs of air correct??when your looking at a fan that looks like blades are missing. Am i making sense or not?
Well why stop there? If less blades cool more, why not run a 1 or 2 blade fan? Should move a ton of air right? ? That advice makes no sense to me
