Please help me diagnose this 273

If it was my car I'd push it in the garage and change the timing chain. The nylon cam sprocket gears will crack over time. And when they do, pieces of the nylon break off the teeth. If enough pieces break off, the chain will skip teeth and then push rods will bend, all the intake valves will bend, and maybe some exhaust valves will bend. [personal experience].

After the chain is installed [double roller is preferred], adjust the valves. Because you have solid lifters, any exhaust valve seat recession will tighten or eliminate the valve lash. If this happens, it is likely that an exhaust valve will burn. -------- good luck -------