Amazing to be learning from the legend himself. I am in my 60s and was reading his books in the 80s. Love the way David uses logic and science as gives his unique knowledge to the world! Thank You Mr. David Vizard!!!

I bought the book a few years ago and watching the videos and reading DV's book really helps to understand all the info pack into making HP.

Hey David. Not to go to far off subject but, recently found the guy you must of been talking about when you said "There are people out there who grind cams that think LSA is unimportant"... Found the guy and those were his words...Wow!

Thanks for the video. Best tech anywhere. I would like to thank Al Gore for inventing the internet. Well done, Al.

@montebradshaw128

Ай бұрын

Absolutely true!!!

@montebradshaw128

Ай бұрын

I meant best tech anywhere! Lol

@dennisyoung4631

Ай бұрын

DARPA, actually… This information *is* the best.

@waynecrumblin4764

Ай бұрын

Wasn’t it Tim Berners- Lee the man that made the internet communicate?

@larrynorsworthy8582

Ай бұрын

😂

Sir…. You are a living legend. You never cease to amaze me with you technical knowledge. I always look forward to your videos . God bless you . May you live for another 50 years and teach these know alls a thing or two….👍🥃🇦🇺

Thank you David! For all your hard work and knowledge you share, we are so lucky to have you sir....❤

I've had that book for a very long time DV, and have read it cover to cover a few times Alot of great information on porting and friction in that book also

At first glance it looks like your chart oversizes primaries. Gordon P Blair ran a design of experiments and came up with a 1.5" and a 2" primary making the same power. Drag racers might run a 1-7/8" stepped primary for a 900 bhp small block, where you'd suggest 2-1/8". One Nascar team uses a 2" primary, and I guarantee the exhaust flows more than 220 cfm. That may not be "ideal" in your estimation, and I'm sure they've tested more than one set of headers.

So any idea why the video stops at 23 odd minutes and continues for 12 more minutes of blank screen and hacked up music bits?

If there is one tool to grab and use for building an engine, its the primary sizing chart DV has published. Easy and... it works. Maybe an experimental fuel engine might escape its recommendations, but not likely, and not by much.

Thank you so much for REAL quantitative, information. Well Done.

Please keep sharing your knowledge the world is a better place with you here.

Again this is wonderfully well explained and it opened my eyes to a different way. Thanks again for your video.

Thank you David for another interesting and educational video.

Thanks David. Maybe length and extensions next?

@johnpublic168

Ай бұрын

length is simple street towing as long as possible. racing 8 to 10k rpm 23 inches and 18 inches

@dondotterer24

Ай бұрын

@@johnpublic168 drag and drag car.N/A.600 hp or less.I can flip the extensions around. I have long tube headers for it. They are 1 3/4. 421 Small block Chevy..I might have to change that?

@johnpublic168

Ай бұрын

@@dondotterer24 421 are very good run them and then compare with 4 into 1 the most important is the collector length start at 3 to 5 times single cylinder volume

Great information, most people just buy them easier, thanks for sharing, all the best to you and your loved ones

Thanks, great information. About to get into building my first set of headers for a tbi 350 gas mileage build. This definitely helps me decide what size primaries to use

@greenman7yyy

14 күн бұрын

Hi, What do you mean by gas mileage build ..)

@jakobsimmons9997

14 күн бұрын

@@greenman7yyy I mean a suburban that gets 20+ miles to the gallon highway out of a tbi 350

@greenman7yyy

14 күн бұрын

@@jakobsimmons9997 I've had one vehicle that used a Magnum 5.2l, put over 350 to the ground and made 24 mpg on the highway. It used a set of Doug Thorley long tube headers with a custom 4" exhaust in a 94 Dakota extra cab long bed...way lighter than a Suburban, which is essentially a brick on wheels. I feel you have made a real challenge for yourself. What have you done to this motor to expect over 20 mpg ..)

@jakobsimmons9997

14 күн бұрын

@@greenman7yyy shouldn't be too far off with a properly tuned set of headers, high power ignition, gasket matched intake & head, raised roof exhaust port and a custom tune. Had a completely stock one in high school on 31" highway tires, got around 18 hwy. This one is lowered, factory ground effects/running boards, switching to electric fans. Shouldn't have much issue getting 20mpg highway.

Thank you so much for teaching us your knowledge. You are a great teacher. Got your building horsepower many years ago and some day I will try to apply to an Oldsmobile big block I got when I was 15. 54 now but they have some great stuff for them now. Again thank you so much Jeff (happy)

Another great video David and a super thank you for sharing this with us ❤❤

Thankyou so very much for sharing your knowledge , im so very grateful . Im a mechanic . Your knowledge is invaluable

You're better than a living legend. Your basic formula for primary pipe size works amazing - I have a Daihatsu two cylinder, four stroke engine with 2 valves per cylinder in a parallel twin. I designed headers with 1-3/8" primary - the exhaust on a standard head is 97cfm. Being as the engine fires once every 360 degrees, I have found that primary pipe length has little effect but I haven't experimented with an anti reversion chamber yet. I hope for good results from that.

Thanks DV. From down under in Australia

Great video hope your back to feeling 1000%

Thank you David, great info!!

Hi, Fluid Motor union is using your zero loose exhaust system idea, looks like it works, depending on where they add it to the piping, they are adjusting sound and or power. Keep up the good work!!

Thanks for the information and the work you have done for us and for sharing it. Can you do a video about your testing, findings, and recommendations specifically on balancers and fleywheels, please, Thank you for all you have acheived and that you share, im soaking it all in and going to be building a 355 sbc and 383 sbc based on what ive learned from your videos and books!

Thanks, David- great info, as always. Any insight as far as stepped primary header sized pipes? Thanks in advance!👍🏻

With the limited sizes of exhaust tubing as seen in the example in this video, the 180cfm head was stuck with 1.625. The 1.75 was over sized for race and the 1.5 under sized for street. Its would be interesting to know Davids though on the affect on the under and over sized. At a guess does over sized loose Low TQ and the undersized loose peak HP?

Im lost formula for a yblock mild build 3200 rpm i got 1 3/8 primarys. For my big block 5500 rpm i got 4 7/8 primaries. Chart seems to match header tests they ran on y block

🔔😎 Excellent. Timely to what I needed to hear. Now, what about the exhaust pipe. 5.0 HO Ford. Under 5000 rpm street performance. Thanks DV and Unity 👍

Simple information, thanks!

Dave if the engine is supercharged will this formula change

great video thank you😊

Great videos, thank you.

I love David Vizard. I hate that annoying creepy music.

@krusher74

Ай бұрын

it was the 80's!!!

One ‘rule’ for the street with a normally aspirated engine is it’s better to be slightly smaller primary than too large. Also the collector diameter is super critical because if it is too small it can/will artificially limit your peak torque RPM …and as a result it can lower the horsepower trajectory ( rate of gain per 100 rpm.

I would like to build some anti-revesion headers. What are your thoughts on the old school ar's with the cone at the header flange vs the new style with the ar feature at the collector? I very much appreciate you sharing your knowledge! Also your How to build Horsepower book is a must read and must study!!

@David Vizard; @DavidVizard; Thank You again for another prepared, recorded, compiled, edited, posted video production within another important concept, wtih clearly described, defined, conveyed principles including visual presentation which certainly includes the important, useful graph. 😄 Perhaps someone in Your production team will handle, correct and re-post due to the video length error in which visual portion of the video with the closing, actually ends at 23:10, but continues with blank, black until the posted 35:34.🤨 All The Best😊, Sincerely☺

halfway trough video, i had to ask; The Ford CVH 1600 engine i had have build, had some very large exhaust ports as came standard. So i could not or could go under the I.D. size of 36 mm. Primaries. I took I.D. after some reshaping, from D Port exhaust, little more curve in the tight angles of D shape, to 38 mm inside diameter to fit. Running bit oversize valves and a Newman PH 4 cam, it runs good, but how it pulls on a rollingroad dyno i dont know yet.

Many Thanks! God Bless!!! Mike

Hello from Australia

Hello David I have a 1968 302 that is all stock except for edelbrock 289 intake and 500 cfm carburetor hei distributor and stock 87-93 mustang headers right now I have a 2 inch duel exhaust system homemade and 2.25 dynomax super turbo mufflers should I up size my exhaust pipe to all 2.25 to get best results it is for a daily driver thanks

Header diameter is rpm and hp dependant not based off cfm

What I experiment with is different stick grinds,, exhaust plates,,and different flow angles on the header tube s,, it's a lot more, but to much to explain 🏁

Would this work on inline 6 turbo engine?

Thanks great video

Same size or a little bit smaller than exhaust port.

Thanks

Love headers and the loose hair on the rhs of your head David. I presume you must remember that 50 years ago you did a good thing ...plus or minus 20% but think of it as a living component first and then ask questions ⁉️😜😔

541cid flat 6 turbo. Does header design matter before the turbo?

Makes perfect sense

Quick question. I hear rams horn cast iron manifolds aka ‘Corvette’ inherently flow good because of its center dump design lets the end cylinders empty easier. True? I think so……

Great video and easy to understand. Just wondering if this principle would work on intake manifolds as well?!

@jakobsimmons9997

20 күн бұрын

I would think fairly closely, yes, especially with an ITB style setup

I can't get the idea of Lavale nozzle-like diameter increases (in steps) at or after significant "landmarks" (turns, etc) out of my mind. How wrong am I, would this not work? I believe this should (if done right) drop pressure and temperature without slowing the exhaust down, but I'm yet to put it to test

Thank you. How does altitude affect this. For example, the good folks at pikes peak go all the way up to 11000 ft. This will cut the dmair density by 70% give or take. Will an exhaust system designed at sea level still be optimized at high altitudes?

Vicars the wizard ✨ 👍

what about Tri Y pipes?

Thanks for your expertise. Does expected shrouding affect your decision much?

@krusher74

Ай бұрын

does the CFM number care about shrouding?

Thanks!

Works on more 4 cyl. units than you give credit for.

Super thanks David! I studied all your books and this video adds very good info to the HowToBuildHP pages. Would you keep on teaching exhaust tech with anti-reversion tricks, 4-2-1 length , stepped pipes, and how under/over sized pipes affect the results? I would love to know your way to manage all that. Cheers from Sergio / Italy

I'm looking at building a set of 180° headers for the 318 in my truck. I don't want to lose the low end torque by putting headers on it.

@knowbull5hit590

Ай бұрын

Good long-tube headers will add a lot of torque over any stock manifolds

@chevyrc3623

Ай бұрын

I would say don't go bigger than 1 5/8 I am sure that will be fine

@billythebake

Ай бұрын

​@@knowbull5hit590Heck, I found a lot of the time that even mediocre long tube headers are better than the old '60s and '70s log manifolds on mopars Especially the 318, And the low performance big block stuff - they were often saddled with pretty poor manifolds

Great video david!!!! Can i use the chart in your book for a 4cylinder motorcycle engine or a single cylinder atv

@DavidVizard

Ай бұрын

Sure!

@duygukayhanisaskank4915

Ай бұрын

@@DavidVizard D Hey David....THANKS for another AWESOME, informative presentation. PLEASE create a video on the subject of "stepped" header tubes, the importance of exhaust velocity, etc. ALSO, PLEASE, PLEASE, PLEASE include "a bit" about header design for flat-plane crank engines. Best regards, Ben

Hi where do we get the book please share

@DavidVizard

Ай бұрын

Amaz0n - a,s the video says!

At 7:17, "sqare"?

Can scavenging be to great and draw to much raw fuel and air out exhaust?

@briantayes2418

Ай бұрын

You would need to reduce your overlap.

We had them all

David theres 12 minutes of blank video after the closing credits

Notepad ready.

If you want to size for velocity you want to use velocity in the engine, therefore you would use hp per cylinder as a proportionality not cfm on flow bench

@stevecowan1362

Ай бұрын

Yes,agree on your comment. You can not design an exhaust port on the flow bench,the problem will be people will just make the port bigger to chase more flow which could potentially kill the cylinder head reducing power. One of the best header builders in the world Calvin Elston uses hp/ cylinder/ header diameter. Not cfm

@NickGreiner1988

Ай бұрын

Thing I don't understand is, if you don't know the right size for the estimated max HP, then if you test the wrong size you'll get lower HP than is possible, but then if you estimate the HP being best with X size pipes, then test how much power it makes, how will you know if that was really the best power? If you use the power you made again to calculate the pipe size then you may have to change the header size again? Wouldn't you just end up going round in circles? If you can't get to B without knowing A, then how can you know A if you can't get to B first?

@dmc5681

Ай бұрын

@@NickGreiner1988 if you make 520 or 500 the pipe size requirement is basically the same as 1/8” increments is what you choose from. In the end without testing you can’t be certain of anything as these are rules of thumb. All I know is if you choose based on exhaust flow on a flow bench you are choosing based on a scenario/condition not representative of the running engine and if the exhaust port is too big then you perpetuate that flaw by choosing a pipe size based on that single aspect. An engine is a system so consider the whole system needs and a predicted power number if you haven’t got dyno data to plug into pipemax is a better way imo.

I wonder David Vizard think of 180 degree V8 headers

Hello

Pressure differential is what determines gas speed, the exhaust gas temperature is a factor missed here, also the valve throat isnt always the minimum cross sectional area, the minimum cross sectional area will dictate the flow potential of a port, when you recorded 11psi pressure differential during overlap that is a factor of the intake valve curtain area at the time, plus at 11psi the airspeed past the intake valve curtain area would be beyond the speed of sound and in choke. Your chart is just as much of a ballpark guesstimation as the other formula provided.

Algo comment.

🥝✔️

That sizing your chart is inbetween 1 3/4 to 1 7/8 and actually that sizing i have did somewhat a test when my engine was not as good as it is now but i went from bigger tubes to smaller it ran much better and most people are running a step header between 1 3/4 to 1 7/8 which i am getting that size and my engine does like to around that size

@JG-kv4oi

Ай бұрын

What cubic inch is your engine?

@chevyrc3623

Ай бұрын

@@JG-kv4oi 358 I race Wingless Spec Sprint I already tested headers myself and it seems like 1 3/4 step to 1 7/8 seems to be ok

the ONLY WAT TO KNOW IS BUILD SEVERAL SETS,,,THAT IS WHAT THE PROFFESIONALS DO

I calculated my bikes silencers efficiency and got 1380 rpm 😂

Why is the video 35 minutes long but ends at 23 ? That’s weird.

@krusher74

Ай бұрын

its 12 minutes to stare into the darkness as you realize you are never going to build an highperformence engine ever.

These motors weren't in Pinto's

@Dan_moon_sun

Ай бұрын

Are you having a joke

@lt1nut

Ай бұрын

Q: "In Pinto's, what am I missing?" A: "Yep, the British cosworth ones. Pretty cool stuff!" He's speaking of the British/Euro Ford/Cosworth Pinto which was not the same as the US/America(s) Ford Pinto even though/when the displacement was "the same". (There's no need for anyone to jump on anyone that does not know that since that accomplishes nothing positive -- each "side" could just as easily jump on the other for lack of knowledge, understanding, or maturity.)

Not sure if you know this, but the last 12 minutes or so is a blank screen.

And dont forget ST JUDES. 😎

Thank you for your knowledge and videos USA 🇺🇸 TRUMP 2024

David please devote a book to just exhaust please. So much disinformation out there mate. Cheers 🇦🇺

140 episodes, and still haven't leveled audio very well. Please turn down your dramatic music in your edit.

As big as you can fit.

@mikewillett5076

Ай бұрын

Had a 283 with 1 3/4 primaries because that's what I had (where this formula suggests a 1 1/2.) Solid flat 236° @ .050", 195cc heads. Ran just fine and stong but of course 4,000 stall helped a lot. Lol

@krusher74

Ай бұрын

Merica!

Thanks!

Thanks