[cjshaker]

Kids' Playdoh or some sort of clay is what I've always used. You can knead a strip any way you want, lay it across the dome, then after cycling you can slice the playdoh anywhere you want to check thickness with a caliper. Seems like that would be an easier method to measure than using tin foil.



And Tubman is right, keeping the quench as tight as possible greatly improves combustion efficiency of any engine, but especially true on flatheads. You just need to keep overall compression in mind when figuring volume.