Distributor timing

I would like to add something here. When assembling the engine, line up the timing chain marks at 12 o'clock top gear and 12 o'clock bottom gear, this is TDC compression stroke. Once the marks are at 12 and 12, I go down the distributor opening and paint a line on the camshaft that can only be seen at TDC compression stroke not at TDC exhaust stroke. Now you don't ever have to take a plug out to find compression stroke, just turn the motor to TDC on damper/timing mark and look down the dist hole and if you don't see the paint stripe then turn the engine 1 revolution! If you set up the timing chain like the book says at 6 and 12 the distributor will be 180 degrees incorrect.