Thanks heaps Will!!

that helps a lot. What rpm’s are you pulling as well? I might drop my aluminium head shim then!

I’m currently running 15% nitro, 20% cool power blue oil, aluminium shim, os8, Bolly EQ63 pipe, 510mm from piston face to first baffle (following bend of header), Bolly 12.5x11.5W prop, around 10,300 rpm but I’m not sure if it’s getting hot at that. True piston/liner set too.

mine didn’t like the 13x9 apc, but thinking pipe may have been too short?