No Compression

Not likely the valves hit the pistons. No need for BB valve springs, with a stock or mild cam. I run 340 springs with dampers on my 170 and can turn 7,000 without vave float.

My sugestion is to put the piston at TDC, and remove the valve springs on that cyl. Remove the old seals, and put MM oil, Kroil, or something like that, on the valve stems. Use a tap handle on the valve stem and rotate the valve as you push and pull the valve, to free it up. If the valves free up install new seals and reinstall the springs. Do each cyl the same way.

If you do need to pull the head, then I would suggest milling the head while it is off. Raising compression ratio is the best single thing to help a slant.