I have 6.4 springs on my eagle heads with an SRT8 cam and it runs great, no coil bind and this is not the first one by any means. I could see daylight between every coil with the lifter bled down then shimmed solid with feeler gauges. Theoretical and actual are frequently different. I have 2 .040 shims in there, 3 and I could barely see light through a couple of the coils.