We used to get a noise like that when the timing belt got loose (tensioner is not self adjusting) it seemed to rattle the distributer gear on the camshaft, also check the small ball race bearing in the distributer, we had one that chewed up the camshaft, I have adjusted the belt tensioner from the top without taking the crank pulley off with a long 14mm spanner (not easy though) just to check, but the belt may be had it.
Cheers - Leigh