Back to basics, ensure the simple stuff is up to scratch. Good working parts such as distributor go forward. Drop in filter, plugs, light freeing up off exhaust. Proper grade oil would also help.
Dave I am presently using 20W50 and for a while now I am experiencing a slight burn off where I have to do a little tapping up like every 3 weeks. It was recommended that I change the rectangular seal in the valve cover which was very hard and brittle. This was just done this week.