Other than completely covering the radiator while warming up the engine on the stand not much else. I get mine to 115 or 120 on the stand and then shut it off and put on ground get dressed and wait for grid release to go on track. fire it up and go easy 1st lap with rad flap down and maybe my hand over the front. I try to run enough tape to maintain 150 min with flap down.
I don’t think this has anything to do with packing blow out. Are you sealing the header with the RTV? use doubled up springs.