Ralph wrote:X-max 300 is bucket over shim but is SOC so
they may be changable without removing the cam
don't know but on some engines you can get a tool
that pushes the valve down allowing you to change the shim.

Seen a curve push tool to get the shim out if shim OVER bucket...

Just looked at the 300 and it looks like the shims are in fact
small buckets that sid on the end of the valve's and if you
cant change them by pushing the valves down that you can
remove the rocker shafts and do it that way rather than
touch the cams, could be wrong but that's how it looks to me.