recurring problem: valve springs are breaking! Please help

I have a 66 with a 289 that I had rebuilt at a motorshop in town and after about 40thousand miles of no problems, three valve springs have broken on me with in about a month of eachother. I replaced one then another one a month later and the third one that broke was the first one i replaced that was new. I made sure the valves were adjusted corectly and the only thing that isn't stock is a very mild cam upgrade. I need help figuring out what this is so I can fix it. Has anyone else had this Problem?
Thanks in advance.


Chad Patten

I never thought about the springs not getting oil. All the breaks have been on the passenger side of the block. I adjust them with the covers completely off and the engine running and inspected all the springs at the time and there doesn't seem to be any binding or bottoming out. If I were to buy a set what set of springs would one suggest? Has anyone ever seen the disk on top of the spings that the keepers lock into that has an offset so there is actually more room for springs to travel?