You won’t believe what fixed my timing marks problem. We decided to use a vacuum gauge to check the vacuum and the needle on the gauge bounced all over the place to where no reading was possible. We also decided to check. Compression. The first cylinder we checked (#5), was zero. We removed the valve cover and noticed one of the push rods on #5 was not positioned correctly and wasn’t moving the rocker arm at all. We fixed that and decided to adjust the valves. Many valves were off including several too tight. We adjusted the valves on all 8 cylinders. After putting everything back together, the vacuum gauge flutter was gone and we had a good steady vacuum. The timing marks came into view where they should be as well. We never thought those would be the problem.