I don't know if this is technical, but I am wondering if the 4-blade fan I got that has the different bolt pattern and will not bolt on to replace the 3-blade fan that is on motor? Would work fine if I drill out the holes and grind between the creating a slot.  Would this cause an issue with water pump life span? The center holes are the same size and both fit snug on shaft.  My concern is would fan be out of balance maybe to point of taking out water pump?  There does not appear to be any balance weights on the fan.  As it rests on the center shaft and bolts then secure it.  Am I just over thing this? Sorry if this is a dumb question. .   

Why don't you just buy the correct 4-blade/6-blade fan?

If the bolt pattern does not match, then the fan did not come from a Y.  As such, ensure that the fan will sit directly against he hub.  Creating slots so close to the center shouldn't cause issues with balance.



Lawrenceville, GA

Is the pitch correct? Ideally, the fan blades should be about a 1/4-inch out from the shroud, assuming you have the original shroud installed. 

As long as the center hole fits tightly on the water pump shaft, then balance is not anticipated to be a problem.  The existing attachment holes at the water pump hub not aligning with those in the fan is easily corrected by either slotting the existing holes in the fan blade or simply drilling a new set of holes.  For the engines I run on the dyno, I sometimes find it necessary to drill new or corresponding holes in the water pump pulleys to adapt a non-application specific pulley for an engine I am running.  Drilling a new set of attachment holes in a fan blade is doable in most cases.  Just like the pulleys, it’s important for the center hole in the fan blade to match the water pump shaft upon which it rides.

Lorena, Texas (South of Waco)

YBlock 4 blade fans should be a "dime a dozen"  Get the proper one.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

For what's it worth. I recently tried a 6 blade fan on a 57 bird and was disappointed with the airflow. Changed to the standard 4 blade and airflow was way more, not even close, at all rpms. Same diameter, about the same distance for the back of the blades out of the shroud. The 6 blade had come from one of the typical suppliers. At least in this case more blades didn't mean more airflow.