Quote Originally Posted by Overkill View Post
I ran an XP on LS6 springs for 3 years in my own GTP. I revved to 6600rpm on the dyno several times, I made 320whp non-intercooled pump gas which was a record which stood for several years from 2003 onward.

I've also used LS6 springs on other XP builds, Intense Stage 2 N/A, S1x, ZZP GT3 (which is two XP exhaust lobes), an Overkill BBC prototype cam with .544 exhaust lift, roughly a dozen Overkill SBC cam with 1.7 rocker setups with .537 lift.

I'd love to know more about why you had issue with the XP/LS6 combo, at least you speak from your own experience unlike most, but I can assure my experience with LS6 springs is that they are awesome, reliable, make the power the cams should, and don't float valves. My more limited experience with CompCam 130#s was poor.
If you expect floating valves to act like a rev limiter then you are rigt... you didnt float valves. You were running into rising boost pressure passed 5500 rpms and stagnant flow readimgs from the maf that wouldnt have happened with the right springs.