engine noise

When I say it's much more noticable under acceleration I mean 0 - 30 mph over a long distance, I don't have to be hammered down. The rythem of the noise is as if it is one cylinder or one lifter. I did advance the timing to 18-20 initial and that pinging was a completly different sound. With all that being said I very humbley give my thanks to all the suggestions and will go through and check every one of them for the possible solution. I ordered a set of remflex header gaskets from vic's today and I will give them a shot as soon as they get here and let you know what I find out. My next focus will be on the dist., it is a mp unit that came with the electronic ignition conversion that I put on the original motor about 15 years ago and maybe the springs are getting weak. My timing is all in by 2K ( probably a little early?).Thanks again!