99% of headers are wrong!

In this, episode 18, DV explains why why header company's are selling you less than optimal headers even when there are no install space issues to deal wth. AS usuall he deetails the fixes that will allow up to 35 extra HP.
Note - you have never seen anything like this before.

[LawrenceTheKiwiBryant]

This gentelman is 100% right on ALL points.
In the early 90's I was a Fabricator in Aussy building V8 Super Cars.
We spent hundreds If not thousands of hours on the dyno and track testing all sorts of header combinations.
We had a 5 litre V8 limited to 7500rpm limit because of CAMS Rules.
So to get every ounce of H.P out of such a small engine took a huge amount of development, even on the intake side also.
We ended up having the engines so finely tuned an 1/8 inch change on just the intake length could cost us 45hp.
All our headers ended up being 4-2-1 with an expansion chamber of the collector to an X pipe, all lengths where based on the heat (Sound pulse) signature of each tube all the way to the X pipe.
If you listen to the engines (Before we had to really muffle the cars) of the higher funded teams (Holden, D.J.R etc) they ALL sound like high reving two stroke V8's, and we where making North of 600h.p reliably all day long.
Awesome to see this dear man share his wisdom 👍🏻

[DavidVizard]

Guy's - I am so busy doing new videos that getting to answer your questions is getting to be really difficult. Hopefully you will get most of the answers you are looking for in future videos.
DV

[markhatch]

My dad was a race engine builder and machinist (Pacific Northwest USA). His career spanned the 1960's through the 1990's. He did a lot of development and dyno testing (mostly V8's of every make). I know he would have been fascinated by your work. We had a customer that went to the trouble of building a 180 degree header system for a C3 Corvette running in the American SCCA Trans Am series in the 80's. The primaries came up and over the valve covers and back to vertical collectors that went down over the passenger side of the bell housing. They made the engine sound like a formula 1 engine. The pounding roar was completely gone! The power improvement was on par with what your work shows (2-4 percent). That's a lot when talking about the tiny margins we fight for in racing.

[erukred]

I learned a lot from David’s books. Very knowledgeable guy with tons of experience.

[stephencarter]

I have followed your career all my life before the web, I sucked up everything you have shared via print and have several of your books next to me right now, Everybody thought Earnhardt could see air move, You were the Pioneer of Air Movement and traction Your my Hero and a Legend. Thanks, David for not keeping your wisdom to yourself and sharing your infinite knowledge, I have always appreciated it.

[gordmckenzie]

This is very interesting; the thing I’m finding is, the more I learn, the more I realize that I don’t know.
Thanks for all you do David to give us your help and years of experience; greatly appreciated, .

[renardsaucier]

Sure, after watching the videos on this 99% headers are wrong, I have to agree with you whole heartedly, I have over 12 years of research and development technology from chemical plants. Understanding what you're talking about is so easy to digest. It is all based on what we used to call a batch process with multiple reactors. And measuring what comes in what's going on through the reaction phase and what is being exitive needs to be measured understood. And then if you're tying all these reactors together, you have to have the ingress. And egress shut up in an opportune manner to where they work in unison to the best yield that you can get, keep the videos up, and I love your work, and I think everybody needs to listen to you and understand your formulas and your pathway to this. But you're right on the money, buddy. Navigator

[garyspoering]

Back in the '50s, Motor Trend or Hot Rod Mag had an article on exhaust pipe tuning with a crayon. Draw a line port to end of pipe, eight individual pipes on V8, with a crayon. This is with the engine warm and the exhaust pipes cooled to ambient temperature. Fire up the engine and run it at the rpm you want peak HP, where the crayon melts is where the pipe needs cutting. I suppose several people would be needed to get this info on one run, or it could take several runs. It might be worth a try to find each cylinder's favorite length. Have not tried it, being a two stroke motorcycle racer, I went with other information.
If you or others try it, let me know if it works.
Good luck on your endeavors!

[n.elliott]

Really connected with your teachings. Understanding building my winning 2 stroke motors with proper pipe/pulse calculated really brought me to you. I feel like I now have a PhD after reviewing all of your videos.
God bless you sir!

[waynep]

I got a friend with an h22 engine honda. No turbo. Did a naphin drawing of a tuning tube to install at the collector flange. He installed it while bolted to a mustang chasis dyno. Picked up 10 hp at 6500rpm 265 to 275hp . Changed the sound from a raspy honda with a lot of reversion slap. After it sounded like a healthy big block chevy. The tuning tube used the inertia of the exhaust pulses to stop the reversion. I think it also increased scavenging in the primary.

[robormiston]

On my 2 stroke racing kart the distance from the piston to the end of the header tube is measured and you can put longer ones on for a different torque curve. Or shorter ones. But it deffinetly makes a difference. This is on my Yamaha KT 100 race kart. I change the h.p from 12 to 16 h.p with different length pipe. On race boats the make tunable headers that move with a lever. Cool stuff. Thank you for sharing your wisdom.

[lancemenke]

The key to getting it correct it must include the most important fact dual plane puts the pulses not even time period for each side. To get the max flow 4 into 2 then collector and the rest all counts. A flat plane v8 is different. The information he is sharing is spot on.

[peteZ]

Great stuff, Sir.
@26:42, you list the length changes for cylinders as:
Cylinders 1, 4, &6 + 4 inches
Cylinders 2, 3&5 - 4 inches
Cylinders 1 and 8 - nominal length
What about cylinder 7?
Thanks.

[metalhead]

Your summary (~28:30) shows cylinder 1 as being both +4" and nominal, and is missing number 7. Which 1 should be a 7?

[CanadianOnlooker]

180 degree headers are the true equal headers. they put the pulses all 180 from the last cyl. sounds more like f1 also, a hum rather than a classic v8 rumble. dude made a set on youtube great video & informative

[thepicklejar]

Thank you for your years of research and passion David. 35 years old and glad I found your videos!

[Sir.VicsMasher]

Somebody needs to ask David to clarify the primary length formula during the next live chat because cylinder seven was left out and number one was repeated at 26:38.

[kevinkirk]

The wisdom of senior mechanic and engineer. Very interesting stuff. I just subscribed.

[lukeperry]

I'm trying to my best to follow this for my upcoming build, and I'm getting a little lost. Basically what we're trying to do here is ensure that each cylinder's pressure wave arrives at the collector in evenly spaced intervals. At 26:35 we see our big moment that gives us the exact measurements (although there is an error here, cylinder 1 is listed twice and cylinder 7 is not listed), and it was in trying to apply those logically that I realized that I was lost. With a classic firing order of 1, 8, 4, 3, 6, 5, 7, 2, evenly spaced at 90* intervals of crankshaft rotation, this doesn't add up in my mind. Please see my diagram below of cylinders and the number of degrees of crankshaft rotation that have occurred since the previous fire of a cylinder on that same bank:

8 - 180 7 - 90
6 - 180 5 - 180
4 - 90 3 - 270
2 - 270 1 - 180

It seems to me that we should be making the cylinders that fire after only 90* should be the ones that are 4" longer, and that the ones that fire after 270* of rotation should be the ones that are 4" shorter, however this does not match up with the "big moment". I considered the fact that this test may have been done with a firing order swap of 4&7 and perhaps even 3&2, but still it's not making sense to me.

Hopefully Mr. Vizard sees this, or someone else who can clear this up and help me understand.

[Melomanisch]

There is a mistake at 28:00 minutes.
Cylinders 1 should be +4 inches and also nominal? One of those should be cylinder 7, right? But which one?