I second the initial timing you should be somewhere between 10-12 initial. 20 seems high will heat you up quick. My linkage was an issue to easy stuff to middle out before dropping any coin.
10-12 is stock, I think he would need a little more, like 16-17.
Also forgot one thing, did you check your rad cap to see if it is good?
Another thing to do might be to try another one with a lower pressure. I forget the formula but for every X degrees of pressure, the boiling point of the coolant is raised like 15 degrees. Or something like that.