OPEN HEADERS LOSE POWER!! But here's why....

A trick that an old drag racing buddy taught me was to add an equal diameter tube onto that flange. say, 22 inches long. Paint it a light color with hi temp barbeque paint. After a few runs, cut the tube where the paint stopped burning up. It is now ideal length,

As a 65 year-old hotrodder, you explained this well and correctly. However, I never uncorked headers to gain power. I only have raising hell and making noise on my mind. Is that bad?

You are 100% correct. Back around 1974 I took my street driven 1970 Mach 1 to a test n tune. I uncapped my street headers and fought with the car all day. It definitely lost torque and was running a good 2-3 tenths slower than what it ran on the street. Being an ignorant kid I tried rejetting the carb, switching carbs and changing the timing all to no avail. It was a turd, especially down low. If only I had had some bolt on collector extensions!

Very good video. You are 100% correct about the scavenging effect and the power pulses. (Same goes for the intake, look at Chryslers ram induction). Our rule of thumb was to install a collector that was painted, run the engine at about 2500 rpm and see where the paint burned off on the collector. Then we would cut the collector at 3" past the paint burn off area. This was back in the '70's when we were doing this.

This is literally the best explanation of exhaust scavenging I've heard. And I'm 53. You nailed the laymens terms explanation method.

I love how the engine on a stand is in the middle of the living room! Legendary my friend

You are mostly correct but there is one part you're missing, scavenging occurs because of a pulse that is sent backwards whenever the exhaust pulse reaches the collector, think of it as a ripple in a pond bouncing back after hitting a dam. Basically you are trying to catch the vacuum on the bounce back, which pulls the air into the cylinder over exhaust and intake overlap, thus creating scavenging. This only happens over a short rpm band, and this rpm band is determined by the distance from the valve to to the collector, and the longer the header the higher up in the rpms you catch the scavenging effect. Now because it works like a wave there will probably be 4 or 5 peaks in torque that you will see in decreasing magnitude, but if you aren't running high enough rpm it is absolutely possible to have too long of headers and so you won't be catching the first and strongest pulse, instead youll be using the second, much weaker pulse. Anyway I hope this helps someone learn something.

I can confirm this information is 100% true. My engine on my 73 ford makes more torque with mufflers but lacks the top end power of open headers. When I tried just running open headers I had great top end power but horrible bottom end torque. When I ran 18 inch collector extensions on my headers I got the best of both worlds. With the extensions I seemed to have way more torque than I did with the mufflers and just as much top end power as open headers and a better throttle response. My car is definitely faster with the collector extensions!😁

I knew this information only because I listened to 5-10 other videos. You, my man, made it almost too easy to comprehend. Very nice.

You should check out the old school Mickey Thompson Super Scavenger headers with the long racing style collectors and mounting flanges for street exhaust systems. The best of both worlds.

That actually makes sense and explains why the H pipe exhaust is good

62 year old son of a former drag racer. I never ran open headers. I had a buddy of my Dad weld up a collector with a wedge to help scavenge an bolted a high flow glass pack to my 428 Cougar. Never noticed even a tenth at the track.

Thanks for this video. This gives me ammo in my arsenal to send my buds who are just not educated on the science dynamics behind what exhaust actually does to performance.

Back in the day I put a big block in my 68 Camaro and I had to run header mufflers for a couple weeks until I could save up the money to get the exhaust system done. I swear the car had twice as much bottom end torque after I got the full exhaust system installed. Back then you had to bring it to a muffler shop and have the system custom bent. I ran two and a half inch pipe with a set of Turbo mufflers. I miss that car so much, I should have never sold it!

I learned something @ 44 yrs old. And I have been around hot rods my entire life thank you. I have so many more questions for you.

Excellent description. I've seen older bikers tuning their bikes with a sliding exhaust listening to the tone change. Take an exhaust off a two stroke it virtually stops.

Great video! You should make another header video that describes the physics how exhaust manufacturers & many authors concluded short collectors are favored for horsepower and longer for torque. Smokey Yunick mentioned in his book Power Secrets how tricky in his attempts with exhaust, He actually figured out ways to find natural low atmospheric pressures under the chassis of moving race cars and "dump" header pipes there. He was genius in many "waste not want not" hp gains.

That's why when I built my own 3 inch exhast system for my 340 Dart it picked up a very large amount of power. The combination of 3" header collectors and 3" exhaust pipes to the mufflers extended the scavenging effect. Mandrel bends and good mufflers lowered back pressure to increase the flow in the exhaust system at all rpms. My previous exhaust system when really examined at its bends was pretty bad.

This is the best video I’ve seen unlike these other videos. You got straight to the point, Thanks man!

Currently collecting the parts to build a rat rod, I appreciate that you not only identified the problem but also offered the solution, that info will be put to use on the build, thank you 🤙🏻