Notice the offset of the pulley vice the flange centerline. The bolts are in shear for driving forces (very light) and in bending for belt tension (slightly higher load) so the little guys are working hard, and more bolts is a better answer. Racers run the single belt with the stock alternator location, and just about 30% of the water pump pulley engaged with no problems at all, so loads are light. I use bolts in all 8 holes with Locktite. If your pumps have only 4 holes, add 4 more and tap. And actually measure belt tension. There are stock two sheave water pump pulleys, where you run the alternator and, or, air conditioning with a two sheave crank pulley. And there is a belt length that you can run the water pump from the Mazda Competition pulley (smaller diameter) with no idler at all and perfect belt tension.

 

No pulley failures since that first one in 1980, (with 4 bolts).

 

Lynn E. Hanover   

 

 

 

There are only four small bolts holding that thing in place … noticed in Haynes pictures this morning that some have four studs and four bolts … guess the studs are for adding a second pulley? – but they would also add extra drive surface area.  I think I put those bolts on with standard loctite but am not 100% certain.  Anyway now I’m wondering if my restrictor plate, loading the pump, may have contributed to more vibration or is this just coincidence …

Jeff