<VV> help needed with engine examination

[gangelli at adelphia.net]

hi everyone I started to fix the starter on my green brier after it refused to start and well you know where it ends up . I had a blowby problem ,engine has only 3000 miles since professional rebuild but did suffer a fuel pump diaphragm rupture in the middle miles .I ran a leakdown test after all cylinders showed 150 psi. well number 5 showed 80% leakdown.I suspected ring problems. after just pulling the head ,i find a bad exhaust valve on that cylinder,but the rings and cylinder look great,stumped since i did not think an exhaust valve leak would cause blowby,I checked the top compression rings after pulling them off a couple of pitons.The ring end gap was .049!!! isn't it supposed to be .017-.025? I suspect all the rings may be gapped too loose.Am I correct in re ringing all the cylinders and setting the gaps at say .020? I hope I do not have to pull the other head . the pistons and heads are heavy with carbon but the engine had a bad blowby so the thing was sucking in constant oil mist . Any other ideas on things to check while the head is off? also found a bad valve cover leak, aluminum valve covers are hard to seal . The bad valve was black while the other exhaust valves were tannish ,I also filled the chamber with prepsol and watched it pour out the exhaust tube  while the other 2 held fine.  thanks for the help . regards jeff agelli