Loss of power with new cam

I am assuming your timing set had only one slot on the gears. Many for small blocks have 3 slots so you can choose 4 deg advance, "straight up" or 4 deg retard for the valve timing. Not sure about slant parts. It can be confusing to find the correct marks that go together (dot, triangle, or square I recall). Some even have 7 slots to choose from. However, I think if you set to the wrong mark it wouldn't run at all. I like 4 deg advance since gives better mileage and low end, plus allows 4 deg wear.

On my small block, I was confused because when the dots came together the engine was at TDC compression on #6, not #1 (was at TDC exhaust). I found that is the way it is supposed to be. No idea why. I don't recall ever changing a slant cam.