Timing

Just installed new timing chain & gears on my 71 valiant with a 225 all stock, with 503,000 miles never been rebuilt been using this car as a daily driver for 40 yr's or so. Anyway I got the dots on the gears all lined up perfect and everything ,she started right up but when I put a timing light on it it's way advanced, turning the distributor only gets it close to the timing marks and is not smooth having it way advanced runs pretty smooth like 30 degrees, I have always ran it 10 to 12 degrees . What happened?