I've read they're two different size clutch fans. I have a 72 340 Motor. I did the clutch fan test where I taped it in place and it did not break the tape so I assume it is not working correctly how do I know what size I need? And where can I get the correct one I've read some aftermarket ones are not quite correct for size dimensions ?
I'd check Rockauto
Rockauto sells the clutch unit separately - transfer the original fan. Interesting they list "non-thermal" clutch fans - description says basically always engaged - what kind of "clutch" is that?
There are 2 types , the hydraulic locking , the fluid expands with heat & locks the clutch .
The second type is a centrifical type so they will take x amount of load & slip above that so they will run at slower than 6000 rpm when the engine is up there !
I like use the first type