Some of the horsepower gain can come down to how well the HP exhaust manifold port is matched to the cylinder head port (and gasket). Guess how much hp you gain by just doing that on a stock '69 440 6BBL to a stock HP cast iron manifold and nothing else? Nick's a good......make that a great guy

First mod I did to my new '69 383 Road Runner back in the summer of '69 was put a set of Hooker Headers on it and they never came off even after "cooking" I don't know how many starters. Never dyno'd it but seat of the pants there was never any doubt there was a performance and HP gain and more than a few tenths better at the drag strip.

Thanks for posting Nick's video! Enjoyed it and all of the other videos he does, stand up guy IMO ..............................Nick should have done a special Moparts only version and LOST horsepower with the headers,

Mike