A full revolution of a pulley is 360 degrees, so180 Degrees out is where, as you know on a 4 cyl engine two pistons are up and two down, the two up, one is on the firing stroke and the other on the exhaust stroke, so it is quite common to find people have timed 180 degrees out (or half a turn) so engine cannot run.
If that is the issue, a quick fix if the HT leads are long enough is to move the leads to the position directly opposite on the distributor cap.
This can get confusing if you are not familiar with the practice, but basically no.1 lead is swapped with no. 4 and number . 2 with 3. this has the effect of moving the timing by 180 degrees.
Obviously the correct way is to confirm number one cylinder is on it's firing stroke and coming up to TDC (usually with plugs out you can put your finger in the hole and feel the compression as you turn the engine with a spanner in the correct direction. Once you know that cylinder is on TDC, if you take off the distributor cap you should see the rotor arm facing the direction of that cylinder lead terminal inside the distributor cap, it is then a simple process to continue to turn until the next cylinder in your vehicles firing order and that will be the next lead the rotor points to and so on.
It may sound strange but once you see the logic it is simple.
As an apprentice in college in 1969 they give us a four cylinder engine with the timing chain off, no valve or ignition timing marks, distributor out and we had to get it running!
It confused some students, but in simple terms, you confirmed TDC on number one cylinder, this then should mean number four cylinder inlet and exhaust valves were "on the rock" one going down and one coming up, it also means on number one cylinder both valves would be closed and with normal valve clearance, so chain was fitted and tensioned.
In that position we then had TDC on the firing stoke for number one cylinder and so could position the distributor accordingly, usually so the points just started to open about between 5 and 10 degrees before TDC.
The principle is the same even on a V12 as long as you know the firing order and can find number one cylinder on compression stroke.