Chev radiator fan

[Phil Waterman]

Hi Wayne & Grant

All three of my CMPs have the six bladed fan, `41 C60L, `42 C60S, and `45 HUP. So I suspect that the intent was to use the six bladed on the CMPs, this seems to be born out in all the manuals I have. The modified conventional Chevys may have had the 4 bladed and I believe this is mentioned in the service bulletins.

As has been mentioned before it is very important when mixing and matching the pulleys and fan belt width to be sure to maintain the relative match of the crank and water pump/fan pulley. Wrong pairing and you can really over speed the fan. With several results, lot more noise, lose of power as the fan tries to pull the truck down the road working as a prop. But more important catastrophic failure of the fan.

When running one engine on the test stand I discovered that in replacing the water pump with a new pump it had the wrong size pulley, much smaller. Started the engine just to check things and at 2000 rpm the fan was howling and blowing so hard it was sucking oil out of the engine breather and spraying it my face. Needless to say shut the engine down removed the water pump pressed of the pulley and replaced it with the correct size.

Cheers Phil