There are ceramic coatings that are applied to the chamber to control thermal dynamics. Techline can do it for you.
https://techlinecoatings.com/
If that isn't your preference, we have a few sets of the 2.4 CIS heads on the shelf. We don't use them so they're not very expensive.
You can buy one or a complete matched set. We can also sell you a completely restored set. New valves, guides, studs, set spring height, etc.
