"409" was inspired by Gary Usher's obsession with hot rods.3 Its title refers to an automobile fitted with Chevrolet's 409-cubic-inch-displacement "big block" V-8 engine.4 The song's narrator concludes with the description "My four speed, dual-quad, positraction four-oh-nine." This version of the engine – at 409 hp, achieving 1 hp per cubic inch – featured twin "D" series Carter AFB (Aluminum Four Barrel) carburetors ("dual-quads"). It was offered in new vehicles (Impala SS ["Super Sport"]; Bel Air; Biscayne) and as replacement units in the 1962 model year.5
It stayed one week on the Billboard Hot 100, at number 76, in October 1962.6
Profile at Songfacts http://www.songfacts.com/detail.php?id=4567 ↩
Breitenstein, Jeff. Ultimate Hot Rod Dictionary: A-Bombs to Zoomies. MotorBooks International. p. 107. ISBN 978-1-61059-235-2. 978-1-61059-235-2 ↩
"The Beach Boys: 409". allmusic. Rovi Corporation. Retrieved 10 December 2012. http://www.allmusic.com/song/409-mt0000107032 ↩
Marion, Doug (January 11, 2008). "40 Years of 348 and 409 W-Engines – W-ow!". superchevy.com. Retrieved September 27, 2016. http://www.superchevy.com/features/sucp-0801-348-409-w-engines/ ↩
Hot 100 – The Beach Boys 409 Chart History, Billboard.com. Retrieved January 11, 2018. https://www.billboard.com/artist/the-beach-boys/chart-history/hsi/ ↩