How can you tell if your engine timing is 180 degrees off without looking at timing gears?

Look at the distributor and make a mark on the housing where the #1 cylinder connects. Then pull the distributor cap. The mark is so you know where #1 is with the cap off.

Next, bring #1 cylinder to top dead center on the compression stroke. The rotor should be pointing at the mark you made.

If you need directions on how to get #1 to TDC on the compression stroke - another topic..