On episode 4 of Engine Masters, Roadkill host David Freiburger and friends beat-up some Hooker headers mounted on a 400-cubic inch V8 to see if the restricted air flow would hinder performance. What they found was that the differences were not substantial, but the internet was skeptical of their study, suggesting that the headers used were too big from the start. Other quips were that the study was flawed because a full exhaust with mufflers was not fixed to the engine, and some folks completely denied the significance of back-pressure.
Having read these comments, the fellas decided to do another experiment of their own. They threw the Chevrolet V8 on the engine dyno, and tested 3 different Hooker headers – 1 and 5/8, 1 and 3/4, and 1 and 7/8. We took the liberty of inserting their findings below:
- 1 and 5/8 headers – 519.7 lb-ft of torque @ 4,600 RPM / 529.7 hp at 5,700 RPM
- 1 and 3/4 headers – 519.3 lb-ft of torque @ 4,600 RPM / 539.1 hp at 5,700 RPM
- 1 and 7/8 headers – 513 lb-ft of torque @ 4,900 RPM / 539.6 hp at 6,300 RPM
But max figures don’t tell the whole story. The smaller 1 and 5/8 headers actually made more horsepower and more torque above 2,800 RPM and under 5,000 RPM, and the larger 1 and 3/4 headers were more efficient above 5,000 RPM. The fact that the engine produced more power under 5,000 RPM with smaller headers should be pointed out to those who think exhaust restriction isn’t significant. And if that’s not enough, then consider the fact that the bigger 1 and 7/8 headers performed worse than the 1 and 3/4 headers across the board, save for the very top end where it made half a pony more.
If all this data doesn’t clear things up for you, try this: put your almost-closed fist in front of your mouth and blow as hard as possible, then open up your fist to let more air pass through. If you’re blowing as hard as possible you’ll feel the difference in your chest, but if you aren’t forcing much air through then you won’t notice this difference. It’s kind of the same concept; that bottle-necking can hinder an engine’s performance.
And if that just confused you even more than you can just click play and have the Engine Masters clear things up for you in about 15 minutes.
Care to give us your expert opinion? We’d love to hear what you guys have to say about this experiment, so sound off in the comment section below.