new motor blues

i've already changed the wires cap rotor ballest resitor had msd wires got new moroso 8mm wires i've even changed #6 wire with another cyl the other one fires but#6 still won't the only thing i haven't changed is coil and orange i've runed it in the dark don't see any fire jumping i'll check the vacume trick tomrrow but with my compression check your saying the valves + rings should be okay how bout headgasket? an enginebulder said to spray the headgaskets with hightemp copper permatex i did but now nobody elese i know has heard of this