I have an Eddy Headed 340... Fought overheating for awhile, flushed everything to the point of popping the freeze plugs so I could get everything completely clean... Tried a couple radiators, shrouds, high flow water pumps, thermostats, tried a viscous drive fan, a solid fan & currently dual electric two speed fans with a shroud....... went through the carb, rejetted a little fat even though the A/F was reading good... Had 14 degrees of base timing & 35 total.... And if you weren't paying attention it would still slowly climb till it buried the needle...
The thing that fixed it I still don't understand.. But after talking with a buddy who's pretty well known for tuning hot rods, his comment some engines don't do what you expect, but they will tell you what they want.... I just accept it...
I increased base timing & it got better... I kept increasing base timing till I had base at 34 degrees.. The distributor advance is now locked out... It starts easily, it doesn't ever ping, it runs great, pulls down 17-18 mpg and it runs 180 all the time....