I added a double groove accessory pulley to the crank damper for when we add AC in the future and now the back of the fan blade hits the outer pulley. Will the cooling ability be reduced if I trim 1/2" off the back of the fan blades to clear the pulley?


Rono

  Ron Lane,  Meridian, ID

I think it would be better to add one of the 1/2" spacer between the fan and water pump pulley if you have enough clearance between the fan and radiator. I had to do that when I added air to my 223 I6, the fan only clears the radiator by about a 1/2" but it's never been a problem, been that way for the last 15 years and I drive in 100+ temps, never a heating problem either.
Edit: If you do trim the fan it will have to be perfect or you will end up with a balance problem..

I had that same idea and bought a 1/2" fan spacer with a 5/8" center hole, but the water pump on this 312 has a larger diameter snout and the spacer center hole was too small. Are 312 water pumps different in that way?

Rono 

  Ron Lane,  Meridian, ID

Car water pump = 5/8" shaft.  Truck water pump = 3/4" shaft.  If the 5/8" center spacer is too small, then you have a truck pump.



Lawrenceville, GA

Like Charlie said you have a truck pump. If your pump isn't fairly new this may be a good time to install a new car pump before adding the air.
Adding air is going to add a strain on the cooling system also so I wouldn't reduce the fan diameter. At hiway speeds it may not effect it but if you are going to be in traffic you want as much as possible..

Turns out the spacer was only 0.006" undersize so I was able to open that up to fit over the end of the pump snout. Now the spacer slides on okay, but bottoms out about 3/16" from the pulley face. Guess I can cut 3/16" off the end of the snout so the spacer sits against the pulley.

Rono

  Ron Lane,  Meridian, ID

Or modify the spacer so it fits properly.
You can probably get your 1/2" only using washers or shims, totally eliminating the spacer.



Lawrenceville, GA

Thanks Charlie! I drilled out the center hole on the spacer so the spacer sits flush against the pulley and the center hole on the fan just barely sits on the end of the pump snout. I now have about 1/8" clearance between the back of the fan blade and the outer crank pulley sheave.

Rono

  Ron Lane,  Meridian, ID

Thats about how much clearance I have also. I have a solid non flex OEM fan and it has never hit the pulley. I don't know if the solid fans flex at all at higher RPMs? My I6 engine  only hits 4000 rpm on rare occasions..

This fan I am using also is a 6 blade solid fan that I took off my 56 Customline when I upgraded to an electric fan. I will never own another "flex" fan. Had one destroy the radiator in my Customline when I got on it hard one day. Carved a smiley face right in the core.

Rono

  Ron Lane,  Meridian, ID