One of the sneaky tricks on the "claimer" 350's we built for the (supposedly) low-budget racing class at Nashville was to put in a .100" bigger diameter exhaust valve and pocket-port the exhaust passages right under the valve. BTW both those mods were highly illegal for the class, as well as angle-milling the low-compression 350 heads we were required to run so they had less combustion chamber volume than a set of camel-hump heads. All the casting numbers were "legal" and the tech inspectors were dumber than a box of rocks, so some of us took advantage of the situation. In NASCAR, "It's only cheatin' when ya get caught!"
Jerry