[rich weyand]

The other TDC is when the piston is completing the exhaust stroke and starting the intake stroke. The intake valve will open before that other TDC and the exhaust stroke will close after that TDC, so they will both be open at least a little. But there won't be any push on your thumb over the spark plug hole for that hole sequence of the exhaust stroke coming up and the intake stroke going down. Only on the compression stroke coming up to the correct firing position TDC will the piston push your thumb off the hole.

The fix for being 180* out is to bump the crank until the distributor rotor points to #6 and the crank is at TDC, pull the distributor up and rotate the rotor 180*, then lower it back down and clamp it. The rotor will move as you pull up because of the spiral gears, and then rotate back as you lower it, but it should end up pointing at #1. The tang on the bottom that engages the oil pump should drop right back in because it is a slot across, like a blade screwdriver.

Actually, you can pull up the distributor in any position, rotate the rotor 180*, and drop it back in, but if you do it with the rotor at #6 and the crank showing TDC with the keyway (or with the timing wheel lined up at TDC assuming it is on right), then you know you are in the right spot going back in when the rotor lands at #1.