[bobcowan]

hard to tell from the pictures. But it appears that the fracture occurred where the push rod contacts the guide plate. The straight push rod looks like it has a smaller diameter in that same area. That means the original builder made a big mistake, and used stock push rods instead of hardened. once the rod wears, it creates a weak spot, and simple spring pressure will cause it to bend.

This should not be that big of a deal for you. Go to summit and buy some hardened push rods for your engine. The diameter depends on spring pressures. If you're using a mild hydraulic roller cam, with matching "light" springs, then a stock diameter rod will be fine. But if you have higher spring pressures for a "bigger" cam, then get the heavy walled Magnums, with an increased diameter.

Bigger is not always better. Bigger rods are heavier, and the increased mass can cause valve float unless you also increase the spring pressures to control it. Unless you're running it to the redline, it's probably not that big of a deal, though.

Repalce all 16 rods. Otherwise the same thing will happen to all of them eventually.

Finding the proper rod length is not that difficult. Take a look at the wear patterns on the valve tips. If they're wearing in the center of the valve tip, then the geometry is perfect. If the wear pattern is off center, you'll need to evaluate the geomtry and see what needs to be changed. Lots of info on that here and elsewhere on the web. IIRC, Comp Cams has a good tech article on that.