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

open header power? not without collector extensions......here is why!

[fuzzyfireman]

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,

[edwardduque]

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

[ronarmstrong]

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

[killerkane]

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?

[terrymeyer]

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.

[llgpe]

When a fella has an engine on a stand in his living room, listen to everything he says about engine building. That’s hardcore. A guy who knows his shit

[danmyers]

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!

[kylesebring]

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.

[dang]

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.

[Corsavette]

This is very well explained. Another thing here, when the exhaust (gas) scavenging is less efficient, so is the heat scavenging from the head (Referred to as waste heat, QC, in determining thermal efficiency of a heat source, n(efficiency)=W/Qn, or, (W/Qn)=((Qn-Qc)/Qn), or said, Work in Joules over Resevoir Heat (in) (Engine) (Joules) equals Resevoir Heat (in)(Engine)(Joules) minus Resevoir Cold (Header outlet)(Joules) over Resevoir Heat (in)(Engine)(Joules). Increasing exhaust efficiency with the longer header add on also increases heat transfer efficiency and therefore contributes to added power/torque. By increasing thermal efficiency, we can increase the Work (W) produced, and if we produce more Work in Watts...then we create more HP. 746Watts is approximately 1 horsepower.

[Samsgarden]

Having an engine in your kitchen gives you more power

[chrisloveall]

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

[monadking]

That's why I made longer collectors to my headers, tapering the pipe down to my exhaust pipes. Great breakdown and explanation of scavenging the exhaust pulses.

[daffyduckling]

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!😁

[crazyhorseracing]

I've always been told that an 18" extension is the sweet spot on most headers... Thanks for the video!!

[shammon]

Finally an explanation as to the reason my bike is after firing. The pulses you explain in the clip cause a vacuum in the exhaust flow and the multiples small leaks I have found in the header pipe manifold then draw air into the straight through exhaust and cause the popping. I welded these small leaks and no more popping, great clip thanks.

[andrewhoward]

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.

[tonypitsacota]

Wow, thanks for sharing your knowledge. What happens if you have that open head without any header or manifold?

[dominickserignese]

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!

[blahbadyblah]

Scavenging effect goes all the way up to the next intake charge (camshaft overlap). Also, you can use white fingernail polish to draw a line on the collector extension. Make a few full throttle passes and cut where the white turns brown.