350 hp out of a fairly stock 340

wawarnick said
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]
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It wasn't "dead stock". They used machining operations that the factory never did (honed with a torque plate bolted on,etc), it had a bowl hog ran through the heads and it had roller rockers installed. Essentially , it was blueprinted. Attention to detail and precision machining makes a difference. The factory just kinda threw them together.