J Heads

I have never heard anyone state that the second ring on a KB piston should be gapped anything but stock gaps. The KB instruction sheet that came with my KB107 pistons had a very good explanation as to why the the first ring needed additional gap and why the second and oil rings did not.

Basically because of the position of the ring on the piston and the piston design the top ring runs much hotter than in other pistons which requires the gap to be larger to prevent the ends from butting and breaking the ring or piston. At temperature the gap is the same as what it would be in another piston with stock gaps. The second rings is not exposed to the added heat so it does not require the addtional gap.

I'm running the XE268H cam in my magnum headed 10.6:1 360 and the engine is a screamer in the 1500 to 5500 rpm range with a dual plane manifold. If you want good performance on the street in the 3k-4k range you mention this would be a good cam choice.