What you're hearing there is sixteen very angry little cylinders arranged in a vee, each one displacing just under a hundred cc's, being force-fed air from a supercharger drawing through a pair of SU carburetors. The result was six hundred frantic horsepower at twelve thousand ear-piercing RPM.
It was basically a pair of 750cc V-8s end-to-end with the thicket of shrieking straight-cut gears driving the dual overhead cams smooshed between them.
And it sounds glorious.
.
