Best small block book

I'm a complete rookie here but I think your problem has to do with the bronze guides. A friend of mine had a small block Chevy a while back and the same thing was happening to him with bending the push rods and valves. The motor ran great until it ran for more than a half hour or so and it got heated up. It would also run good if he didn't "hotrod" it but as soon as he got on it the thing it would fall apart.

My buddy and his motor guy chased the problem for a month or two but I want to say in the end when they finally figured it out, it was because they didn't have enough clearance in the bronze guides for the valves. I think they said the bronze expanded more when they heated up than the regular guides. I'm guessing here but I'll give the guy a call and see if I'm remembering correctly or not.

Good Luck!!