Either bad sealing (hence a compression and a leak down test) or bad valve angles/sunk valves (should never be an issue when installing oversized valves). You had stated that you weren’t completely sure of your compression. You will need to get your actual chamber, head gasket, and piston (+dish-dome) volume and double check. Often times, even with zero deck, compression doesn’t meet expectation because ChryCo head volumes tend to be larger than stated.