Editing Chevrolet big-block engine (section)

==Mark II==
The so-called Mystery Motor, known internally as the Mark II or Mark IIS, is a race-only engine produced for the 1963 season.<ref name="Mystery Motor">{{cite web |url=http://hotrodenginetech.com/chevrolet-427-mystery-motor/ |title= Inside the Mark II Mystery Motor |date= 27 March 2017 |publisher= Hot Rod Engine Tech |access-date= 6 June 2017}}</ref> Development began with a {{cvt|409|cuin|L|1}} version (Mark II) and ended with a {{cvt|396|cuin|L|1}} variant; however only the {{cvt|427|cuin|L|1}} engine (Mark IIS) was ever raced. It gained its nickname due to the speeds cars equipped with it attained during its debut{{citation needed|date=April 2025}}, being considerably faster than the well known W-series powered cars. The engine was first used in [[Mickey Thompson]]'s Z-06 Corvettes at Daytona in the 1963 Daytona 250 Miles – American Challenge Cup,<ref name="Hot Rod">{{cite web |last=Gillogy |first=Brandan |url=http://www.hotrod.com/articles/mickey-thompson-z06-mystery-motor-stingray/ |title= Mickey Thompson Z06 Mystery Motor Stingray |publisher= Hot Rod Network |date= 10 September 2015 |access-date= 16 September 2016}}</ref> and then in [[1963 Daytona 500]] where the number 13 car, driven by [[Johnny Rutherford]],<ref>{{cite web|url=https://www.racing-reference.info/race/1963-07/W|title=1963 Daytona 500 Results|access-date=April 21, 2021}}</ref> finished four laps down (in ninth place), with the top five cars being the heavier 1963 [[Ford Galaxie]] 500's. This "secret" engine was a unique design incorporating aspects of both the W-series and the mid-1965 introduced Mark IV,<ref name="Mystery Motor"/> referred to in sales literature as the "Turbo-Jet V8".