After many hours on a flow bench, designing "Adjustable Roller Tip Rocker Arms", all for the ole "Nail", although the exhaust does have it's limitations, in a normally aspirated situation, it's NOT the exhaust that's the restriction & for many years the popular belief's, but the INTAKE!!!!!!!! Get the AIR in & it has no choice but to go out. Max got the "Nail" to run good & that's where he concentrated his most efforts in the design of his aluminum heads. Buick never did any experimental work with overhead cams, but they did get involved with aluminum heads, big port/d-port heads & turbo's. 39Cent is correct with the "Pent Roof" combustion chamber. Many of today's higher performance engine have this. So what's old is once "New" again. It's because it's a very efficient design that can run higher compression with today's "Quality" fuel without the drawbacks. Contrary to popular belief's it is a "Hemi" in it's own rights.
Tom T.