Once the shims are installed for break-in, you do not remove them. The proper shims should be installed no matter if you break-in an engine or racing. The only time you add or remove shims if you are planning on going to a higher or lower nitro content.

I always let my engine cool down between each tank. Just like the earlier post. Take your time "If you rush this process... your engine will rush it's performance."


Pass you soon...