Agreed, with the head on its side with ex ports on top then with the intake ports on top pour some solvent in the ports & see if it gets wet at the valve heads. I read/saw something (on the dark web) so it has to be correct! that lapping is old school/obsolete & the article went on to say that the contact area will change drastically once it get hot so it is ineffective but I would think that yes heat is going to alter things but I'd want a perfect seal as I can get in the beginning for a good baseline. It does give a good pattern on the height/width of the contact area.