These are not drop in, they require machine work. Refer to pictures for machine work required.
12v Dual Valve Springs
Requires valve spring seat and seal modification (tooling available)
Spring seat can be cut with Comp Cams 4716 cutter and Howards 92085 pilot.
Valve guide can be cut with Comp Cams 4715 cutter and Howards 92085 pilot.
We suggest using Comp Cams 511 seals.
Most machine shops can cut your head to fit these springs.