300se tapping noise

[redrocket]

need some help on this one,have loud tapping noise in back of engine on my 89 300se,sounds like lifter but replaced all lifter's,still noisy,looked at cam lobes,they look good,sounds like # 5 or 6 cylinder,just started about 10 days ago,i tried swapping lifter's no luck,put old one's back in #5&6 cylinder's ,still noisylooks like plenty of oil getting there,i also reolaced all the ball cup's at valve's,everything looks good,cylinder head done about 30,000 miles ago with new valve guides and seal's and valve job,the engine runs great just loud tapping ,maybe rocker arm's bad although there free moving and clean,any help on this would be greatly appreciated,dont know where else to check,engine does have 280,000 miles on it but doesn't smoke or leak.