This is an eye opening test/myth buster. Comments?
https://www.youtube.com/watch?v=azPK...ature=youtu.be

 

Surprised me a bit for sure! I thought the damage at the end would have made more of a difference.

 

Wow, that was unexpected.

 

As oldcutlass (Eric) puts it - "There is nothing that can't be solved with a suitable amount of explosives!" - in this case a "Hammer"

 

Would it be safe to say that individual header tube sizes are usually larger then they need to be?

 

That was interesting. I can only assume that the inside pipe area remained the same or close to it. Smaller in one dimension but grows in the other when squashed. Sort of like oval tubing.
Very cool

 

I feel much better about my 3/8" customization over the bell crank!

 

Once again, subsonic aerodynamic flow is NOT intuitive. I'll also point out that the ports are more restrictive than even the dented header tubes. The intake manifold runners are also more restrictive than dented header tubes. Of course, it's a cumulative problem, so less restriction is always better.

 

Joe I fail to see how intake runners have anything to do with exhaust? The exhaust event produces a huge increase in pressure. At this point the intake valve is closed.

"As the exhaust valve opens, the relatively high cylinder pressure (70 – 90 psi), initiates exhaust blowdown and a large pressure wave travels down the exhaust pipe. As the valve continues to open, the exhaust gases begin flowing through the valve seat. The exhaust gases flow at an average speed of over 350 ft/sec, while the pressure wave travels at the speed of sound of around 1,700 ft/sec."

Explain please

 

The important metric is not pressure, it's mass air flow. Every gram of air going out the headers had to come in through the intake manifold, and the time to fill the cylinder is just about the same as the time to empty it.

 

One other comment. I wasted 15 minuted of my life to watch that stupid video when the data could have been presented in a simple table that took seconds to understand. The whole sequence of beating on the headers with hammers may have been therapeutic for them but didn't do anything for me.

 

It was dumb but that's TV these days. Had to find something to fill the time slot up with. At least it didn't breakdown into a Reality (yeah right) TV Show where everyone yells and screams and they pass it off for everyone's real day to day life.
Was still informative even with the fluff

 

Silly video. Beating on pipes does not change the cross sectional area unless you start creasing them. Gearheads are to engineers like herbalists and osteopaths are to MDs.

 

The problem was the misconception that headers with dents lowered the HP considerably. This has been an old wives tale as long as the Cutlass S being different. I posted the video because it shows that beat up old ugly headers still work fine. Nothing more.

 

So dented cheap headers are still a good buy!Plus dented headers are cheap for the guy who is short on cash. It helps to out the myth that a header with dents will cost a lot of hp.

 

Sorry, no. Do the math. Circumference of the pipe is fixed. For a fixed circumference, a perfect circle has the maximum cross sectional area. The more you flatten it, the smaller the area. At some point you flatten the pipe completely and area goes to zero.

What is happening for small amounts of flattening, is that you are creating a local venturi, no different that the ones in the carb. Airflow speeds up as area goes down, so mass flow stays relatively the same. There is a small increase in friction drag, which is the reason for the small drop in HP. As the amount of restriction (and thus friction drag) goes up, HP goes down even more. It's a cumulative problem.

 

I'm going to dent my headers just to the point of the first test and gain some power in my under powered smog 76 350 haha.

 

You do realize that this is a reality show. Right?
It makes me so mad when I hear some one on those shows say something like I hope so n so doesn't find out about this. Really? Do you think he didn't read the script?
Railguy

 

Doesn't adding fuel and then igniting it in the compressed air volume actually increase the volume of air that then has to exit the cylinder? It is obviously under more pressure than the intake of a normally aspirated engine. Suck, Squeeze, Bang, Blow, right. I don't think most streetable engines are going to reach maximum capacity of a header tube anyway. They were making some pretty ragged dents too. Most of the headers that I have seen that were "massaged" to fit were done with a pipe as the dolly, not a cross-peen hammer. Smoother dents will make even less of an impact on the air movement and speed through the header tube than the creases they were making. And as Joe pointed out, at some point you can actually begin to close off the tube if you flatten them too much and that would reduce power.

 

Again, volume is not the issue. The volume of a gas increases dramatically if you heat it. That doesn't change the MASS of the gas in that volume, and it's the mass of air in AND out of an engine that makes HP. This is why EFI systems have a Mass Air Flow (MAF) sensor. Gas is compressible, so volume doesn't affect flow (to the first order); MASS FLOW (lb/hr, or more correctly, grams/min) does.

 

haha unbelievable. i was worried about the small dent to clear my frame