Engine still not right after timing set

Went through that with a 340 recently. Should be able to get the plugs out without pulling the headers. Run a compression test, leakdown on the low cylinders if there are any. We had two bent exhaust valves that showed up nicely on the leakdown. They weren't bent by much and the engine ran ok, just couldn't get it to burn clean or at the timing I wanted. Also turns out it had a .509 or similar cam. We replaced that, as well...