Hot rod got 320 HP out of a dead stock 340, and 352 HP replacing the manifolds with headers.
"On factory claims of 275 horsepower at 5,500 rpm and 340 lb-ft (3,200 rpm), we got 320 horsepower at 5,500 rpm and 368 lb-ft at 3,500 rpm. So it's clear Mopar understated the facts by 45 horsepower and 28 lb-ft. Then we replaced the manifolds with a set of headers and got 352.1 horsepower and 395.9 lb-ft (at 3,200 rpm)—77.1 horsepower and 55.9 lb-ft higher than published peak claims."
How Bad Did Mopar’s 340 beat Ford & Chevy? Shocking New Data!
[URL]https://www.motortrend.com/how-to/bad-mopars-340-beat-ford-chevy-shocking-new-data/[/URL]