[Dwight Southerland]

The 492 angle plug head was merely the 492 casting with the plug hole machined at an angle. The 492 casting was the last casting that is a replacement for the "double hump" Chevy head. It share the same port and other characteristics as the 186, 041 and 441 castings - accessory mounting holes on the ends, crankcase vent holes between the pushod holes, temp sender hole beween the exhaust ports. It used the classic "64 cc" combustion chambers and was used as a replacement for all the high performance engines back to '61. Some were machined for 2.02/1.60 valves and pushrod guide plates with screw in studs, some were not. Over the counter purchase mostly. That casting was used for the first "off road" offering of a high performance head with angled spark plugs.
The 292 head got its name from the rumor that it was developed for a supposed Indianapolis stock-block engine program that Smokey Yunick was involved in that included a small displacement (209 ci) engine with turbochargers. It has the classic combustion chamber but was cast with much more material in the combustion chamber and ports. The as-cast port shapes were considerably changed from the previous castings and it became the basis for hot rod cylinder heads for several years. This was the first true factory race-purposed small block head from Chevrolet offered over the counter. Smokey Yunick's book discusses the origins of the casting some.