Editing Pontiac V8 engine (section)

===421===
[[File:1965 Pontiac 2+2 coupe 421 CID tri-power 8-lug 4.jpg|thumb|{{cvt|421|cuin|L|1}} [[Tri-Power]] in a 1965 [[Pontiac 2+2#1965-67|Pontiac 2+2]] [[coupé]]]]

The {{cvt|421.19|cuin|L|1}} was introduced in 1961 as a dealer-installed Super Duty option for racing. Unlike previous enlargements of Pontiac V8s, it did not replace the 389. The first of the "big journal" Pontiac V8s, it had a bore and stroke of {{cvt|4+3/32|x|4|in|mm|1}} and came with dual four-barrel carburetors. It featured {{cvt|3+1/4|in|mm|1}} main journals (which the legendary [[Smokey Yunick]] reputedly left Pontiac's engineering department over). The 421 SD became factory installed in 1962 and in 1963 a street version became available from the factory with a dual four-barrel or three two-barrel [[Tri-Power]] carburetion. Modified versions of this engine were extensively used in [[NASCAR]] [[stock car racing]] and [[drag racing]] competition. The premier SD 421 cylinder head was the late 1962-early 1963 casting #9771980 aka "980", featuring a larger {{cvt|185|cc|cuin}} intake port volume, flowing {{cvt|230|cuft/min}} at {{cvt|28|in|0}}. The 421 HO (High Output) was introduced in 1964 as Pontiac's most powerful engine, replacing the 421SD as Pontiac had to discontinue their racing program after the GM board decided that all it's divisions had to drop out of racing.