Good question! I've had harmonic balancers that just only have the top dead center mark. I just go very opposite of it and put a little dab of white paint and then do the same thing go halfway between the two and put a dab of paint on each side. It doesn't have to be way way over exact. The method that I mentioned has you at the very center of the base Circle directly opposite full lift. I'm sure you could be off an inch either way on the harmonic balancer and still be way on the bottom of the base Circle as it's called. (The part with no lift at all)
