440 engine build failure

I have broke in cams with double springs but the cams were under .600 lift and not major pressure and never had a problem. I know it recommended to remove the inner spring, but they always fire right off and 2500 rpm, I use Joe Gibbs grease and a good high zinc oil mostly diesel 1200 ppm zinc but they have dropped some zinc to 800 or so, the stuff is changing all the time.