I was coming home from work, and the motor started sounding odd. Sounded like an exhaust leak. Cam home and put my stethoscope on the valve covers. Pulled one off and after some investigation, noticed a broken valve spring. I lookes like it held but the valve up prett well, but I am a little worred that the valve may have touched the piston. I guess the only way to tell is a leakdown check after I replace the spring. The motor: 331 SBF with Trick Flow heads. I had these heads on my 289. I had them freshend up for the new motor. He put in new springs for the hyd roller cam. I'll have to dig out the cam specs. They are single springs with dampners. It broke in two places. I'll have to check the milage, but I dont think these springs have more then 10k on them. Why do valve springs break? This car does not get driven hard. I dont think I have gone through all 3 gears flat out with the new motor. Should I be replaceing all 16 springs? Or was this just a weird one time thing and I can only replace the broken one?