[Mgs] valve adjustment

[sdesalvo at frontiernet.net]

I am having difficulty trying to adjust the valve on #6 rocker on my "78 MGB. I have replaced the rocker itself, but it is still noisy. Something  I have tried is to slide a feeler gauge into the gap while the engine is running. That quiets it to a normal level. Could it be a worn valve, tappet, cam lobe? The big question is whether I should pull the head at this point to investigate further? Any advice would be appreciated.
Thanks,
Sam