slyws6

OK on a cold startup my car nocks really loud, I can hear it in the house, but once it is up to normal operating temp the sound is gone. Here is the ordeal, this didn't start happening until I broke two rockers on the 5.3 heads I had, car backfired through the intake cause the intake valve didn't close, did this a few times. I have replaced the heads, new lifters etc. and the nock sounds like a rod nock but why would it happen only on cold startups, no matter what the temp is outside. Any idea's.

-Sly