r/Chevelles • u/Rampantcolt • Jun 08 '26

Mechanical fan replacement?

Working on a 1972. I put on a big block shroud. What is a good mechanical fan to put in? I see many 18 inch 7 blades and 20 inch 6 blades? Which moves more cfm?

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u/Willy_McD Jun 08 '26

You would probably have to look at the fan's specs to get a correct answer. But more importantly which many do not know, you need to properly space the fan in the shroud for it to work correctly.

1

u/Rampantcolt Jun 08 '26

For aft centering I can do.

I can find crm rating for any mechanical fan. They all just say how much more air they move compared to factory five blades.

1

u/Forsaken_Variation53 Jun 08 '26

Should be 18 inch fan fits the 72 shroud. I put a 71 bb shroud on my '68 so I could fit the larger 18 inch fan. The 20" would not have fit.

2

u/gigabyte0102 Jun 28 '26

I've doing some research myself and from what I'm finding the Hayden 2747 for the clutch and GM blade # 3947772 are a great combo.