Cup Car Headers - a disaster or what?

If you think that the Cup Car guys have their headers really dialed in for the maximum output then think again. If you have spent the cash for hi-end equal length headers then, to avoid a big upset over wasted dollars, avoid watching this video where DV really lets one and all know where the pro's are going seriously wrong on header design. He also gives some charts and graphs that will let you easily (yes easily) spec out what your motor wants header wise not some motor vaguely similar. Once again DV is delivering groundbreaking tech you will not find on any other channel.

[@groomlake51]

I’m a race engineer. David is law and has proven this to me in the real world many times. I can’t thank you enough for being so open with your proprietary insight all the time🙏🏻

[@cammontreuil7509]

Were do you get a degree for that ?

[@doublewide572]

Totally tubular David, the mathematical formula's for tuning the exhaust is permanently embedded in my brain, with slight variations of course. Listening to you is never exhausting.👍

[@lynnrunningdeer7364]

I see what you did😆

[@gordonborsboom7460]

Thanks for piping up. Collective knowledge merging with amassing flow

[@markvanesse113]

Thank

[@lt1nut]

So many tips are freely shared. Everyone enjoys when two are on the same body of work, some enjoy a single one, and most of the huge ones are all gimmick -- mostly for show, seldom perform as "promised", and often hurt. Duals with two tips each can be good looking; the few that scream can be melodic and at times shriek but those that always shriek truly are exhasting and we all wish that they'd pipe down. In the end it's best to simply go with the flow.

[@JC-gw3yo]

We are sponges out here in the desert. Just when you think we have it all figured, here comes more insight... Thanks David for your never ending engine quest

[@landonthompson5604]

Optimal power from these cup engines to me also is being restricted by the rule makers in Nascar, I'd rather be entertained by the skill of a driver feathering the throttle during the end of a fuel run with worn out tires a engine producing 900 hp versus the stupid 650 hp package we are having to be entertained with

[@tadwiltman4875]

I agree... full power, no downforce

[@edfrawley4356]

Right on. I have thought for a while that Daytona and Dega would be much more interesting with less downforce, less tire width, and zero restrictors. Let the big dollar drivers drive.

[@joe-hp4nk]

Throughout the whole episode I was thinking how Smokey Yunick would react to your research on headers. I have a book from the 80s where Smokey at "The Best Damn Garage in Town" specs out a street and racing small block. One spec Smokey talks about is the primary. On street intakes the exhaust must help pull the air/fuel mixture because they don't flow as well as the track manifolds, and the track manifolds need the 2" simply for flow. The small block build is quite lengthy and covers every component. In the end he says "do it my way and you'll end up with 580+ horsepower in racing trim that'll go flat out for 500 miles" That got my attention.

[@hypergreenorganics2161]

I sure wish I could have apprentice with Mr.Vizard. I live to build engines. I watch Powertech 10 when ever I can. Awesome vids! Thank you for a honest and proper education! Your decades of wisdom is priceless. Love your work David Vizard and Thank you.

[@hotrodray6802]

🔔😎 50 yrs ago Mickey Thompson sold sets of 4/1 headers but inside the looong collector the primaries looked different lengths... Not cut off equally. You saw 4 different length pipes. 8 or 10 inches. I always thought he was on the right track. Never caught on.😎 Guess I'm going for tri-y on Fox 5.0 HO soon.😎

[@williamhenk1030]

My dad had a set of those on his 69 Boss 429 that ended up rusting out at the collectors . He went through two sets of different header designs to no avail . He said the car never ran the same again without the Micky Thompson headers. I think they were called Super Suckers?

[@curvs4me]

Genius! I never thought about tuning by length vs running cross over pipes. Pulse timing can be altered using pressure, diameter, and length to time by velocity. A standard x pipe wouldn't work either as the header outlets would have to be timed as well. Easier to keep the exhausts separate to avoid pulse collision. Thanks DV! Another brilliant eye opener. This could be analyzed down to the fraction if you knew the gas velocity by rpm with a certain diameter primary tube. Everything else could be extrapolated to get test units close using theorized timing.

[@cammontreuil7509]

Straight pipe would be easy to measure. Not so with bent pipes.

[@curvs4me]

@@cammontreuil7509 measure the inside turn radius and the outside turn radius then divide by 2 for the length. Time consuming yes, but an absolute necessity if you are going for pulse scavenging.

[@NotSure723]

David, you've really been neglecting us 4 valvers. Polyquad video pretty please with sugar on top!!!!

[@thomasleclair7418]

,,,,,,,,I grew up loving the input from educated elders...At 71 , I am an elder..........To find David is a gift.......He is my elder.........His dedication and work is matched by ,,,maybe no-one else.............thank you David...........

[@pete540Z]

David, at 24:15, do you mean 7 and 8 are nominal length (instead of 1 and 8)? I don't see a 7 anywhere, so I'm guessing you meant 7 and 8. Thanks, Pete P

[@stevenmitchell6347]

Thank you. I've always wondered how builders would say that length was critical for 4 cylinder engines but not v8's when the v8 is just two 4's sharing a crankshaft. I was always impressed with the 4-2-1 header on my 1969 Cortina GT Twin Cam and drivability on the street.

[@Thumper68]

My fiancé says 2 inch’s really can make all the difference as well

[@JG-kv4oi]

I'm looking forward to your video on anti-reversionary properties. I also vaguely remember Smokey at one point drilled a small hole in the primary tube close to the exhaust port, I assume to ignite unburned fuel and increase the scavenging effect. Thanks for all you do for us David.

[@rcamacho364]

I never stop learning about smokey and what he did. This guy tried anything that crossed his mind and I love it.

[@hotrodray6802]

🔔😎👍 Excellent 👍👍 The last 12 seconds makes my cry, Every time. 😎😎 St. Jude's #1 in my book since 1968👍😎

[@garyderian4350]

Pressure waves travel 1600 ft/s, but the flow itself travels 300 ft/s. To move the pressure wave something, say 45 deg of crank rotation will require a change of 1.25 milliseconds. That would be a length of 2 ft to move the wave, or 4.5 inches to move the flow. This is at 6000 rpm (100 rev/sec). 1,7,4,6 would be delayed, and 2,3,5,8 would be advanced. This would even out the flow on each bank with 4 into 1 headers. With try-y pairs, 2-4, 6-8, 1-5, 3-7, the same cylinders would be delayed and advanced to even out the pulses in each Y.

[@brianholcomb6499]

Mr. Vizard, it might be worth a mention, if you change firing order from factory 1-8-4-3-6-5-7-2, it also going to change your exhaust pressure wave graph! So, your pipe length changes, need to follow the firing order!

[@billywilliams6853]

Yes

[@White.Elemant]

Should the list be: 1, 4, 6 are +4" 2, 3, 5 are -4" 7, 8 are nominal? Obviously 1 & 7 got mixed up, and it would seem logical that 7 & 8 would be the nominal ones?

[@jonelford4513]

I believe you are correct.

[@chrisperryman886]

I did a little doodlin' and it looks to me that 3 & 5 should be -4", 4 & 6 should be +4" and 1,2,7 & 8 unchanged, for a 1-8-4-3-6-5-7-2 firing order.

[@douglasnicholls1366]

I scratched my head and moved on the first time I saw this, but I watched it again just now and decided the same as you. David, if you read late comments you might want to fix the chart at minute 26 where 1 appears twice and 7 doesn't appear. Three of us think we have the right answer but want your confirmation. 🙂 I'm not an engine builder and came to you because you have Uncle Tony's respect, but I do find your technology approach fascinating and look forward to your new postings. Andy, good luck to Casper, you may need it more than you think... or not!

[@chriswong1109]

I hope this is correct as I have just completed a system to these specs for my Rover V8 which has the same firing order as the SBC. It is reassuring DV reads out what is written on the chart at 25.15 apart from 7 and 8. I am sure he would have picked up any error at that stage. I can only think it differs from the Big Block Chev book, which I own, because subsequent testing brought about the results he has posted here. I do agree though, the lengths don't seem to even out the pulses, but perhaps the transducer data provided the strongest evacuation with the stated combo. I will get the system on the dyno to see if it exceeds the equal length system it replaced.

[@josephbernhardt6209]

Very helpful. We have been told equal length were the end all.

[@funkiwikid6106]

Hello David. Your name has been respected for a long time and great to find you still sharing the info. Cylinder pressure measuring devices are beyond my pay scale so your experience is very interesting ... I have noticed one anomaly though - in this video from 24:30 you show the pipe length difference between cylinders BUT you have number 1 twice while number 7 is missing ? Can you please correct that to help me understand what's happening there ? Thank you in advance.

[@Sir.VicsMasher]

Yes, I also hope this gets clarified. I was in special ed and still noticed #1 repeating and missing #7.

[@donmathias1705]

Do you ever think folks today are so fortunate to have so many tools available to them. Everything from cnc equipment, measuring systems and data aquasition. On board diagnosis etc. I'm a hands on machinist and fabricator and boy oh boy, the kit available today is amazing. We did most of it but it took so long and was so expensive. It still takes a clever person to use these advantages in a smart way. I think Henry Ford said" thinking is so hard to do and that is why so many fail to do it" or words to that effect. I've been involved with a lot of race cars over the years and surprisingly enough the number one priority was maintainence. We built lots of good stuff but quite simply if a car was to win a championship it needed to be fixed easily, properly and quickly. Rallying have almost no service time. One race and poor result kills a championship.

[@groomlake51]

This theory is 100% real world proven by the cylinder 4-7 swap and the 4-7 & 3-2 swapped firing order. 18436(57)2 oem firing order has 5&7 firing 90* degrees apart causing 5&7 to make quite a bit less power individually. The 4-7 swap makes 187365(42) causes 4&2 to become the problem. The 4-7 & 3-2 swap 18726543 makes 3&1 the problem. The sole reason we do this in a Roots blown application is be cause a roots blower tends to front load the manifold creating quite a bit more boost to the front cylinders. The set back blower roots blown hemi tends to run cylinder 3 the hardest so we prefer the 4-7 & 3-2 swapped cam so we don’t have to stagger the compression down on 3 so much. A Screw blower does the opposite and sends more air to the rear of the manifold on blown alky cars.

[@sc358.]

10yrs ago I had this idea. Haven't implemented it yet. My hypothesis had a lot more variance in length. I also assumed it would be more peaky having a narrower optimum range and perhaps less average torque. I was going to keep it to myself but I guess I'll share. So using a small/big block Chevrolet with traditional firing order (same method on any just applied). So we have 180 degrees between firing on a V8 right so 180 degrees is our baseline. So if you lay out the firing order and look at the degrees between firing from a primary tube's or an exhaust bank perspective and you are looking at the pressure waves between the first and sequential pulses it looks like this (cylinders): 1. 180 degrees 3. 270 5. 180 7. 90 2. 270 degrees 4. 90 6. 180 8. 180 Just lay the engine out on paper, go in firing order, count degrees between firing on each bank and you'll see what I mean. So you find optimum for cylinders with 180 degrees between exhaust pulses... say it is 34" Cylinders with 90 is half or 17" Cylinders with 270 is 1.5x the baseline or 51" So basically the time between exhaust pulses on that header would be even. Pressure waves are what matter and this would make logical sense. However I'd assume a narrower operating range if optimized. Differences then lie on the intake. So depending on how much sharing occurs would change how much you'd have to tweak it. But I'd assume the 3 sets of different lengths would get you there. Also since half the engines cylinders are the baseline 180 degrees between firing on that bank, the equal length header with the best average power on the primary test comparison would likely be a good proxy for those cylinders and % used to make up the rest. Primary length bank 1 1. 100% 2. 150% 3. 100% 4. 50% Bank 2 2. 150% 4. 50% 6. 100% 8. 100% Just a hypothesis. Needs testing.

[@danielmalone3463]

Hi David, Just going through a few things in the video. Your cylinder numbering for which to lengthen and which to shorten lists #1 twice and skips #7. It also doesn't match the photo of the 572 Chev- your text says shorten #2, #3 &#5, yet you show #5 being extra long. Can you please explain/clarify? Thanks!

[@ericschumacher5189]

Hello David; I have a few questions I didn't see addressed in the comments already, if your willing to share. 1.) Would the effect of adjustment of the primary lengths be "roughly-transferrable" to a header with 4-2-1 collectors instead of 4-1? 2.) Would the Big-Block Chevy (from results you shared), benefitted from 4-2-1 collectors added after the length modifications?? 3.) Based on the above 2-questions, I'm trying to understand if for a 6500-RPM engine if BOTH 4-2-1 + unequal length = MAX benefit??? Thank you ahead of time for any guidance you provide 👍

[@bobqzzi]

I had TFX cylinder pressure measuring unit from Clint back in the day. Very useful

[@gristlevonraben]

It makes a lot of sense. Also, I've always wondered if putting a long swirling design into the pipes lining, like that of a rifle, would cause enough spin of the air to help speed out the impulses. Very cool video. Thank you for sharing this.

[@cammontreuil7509]

It works when you do it with a carb spacer.

[@DANTHETUBEMAN]

15 to 20 HP and torque across the reve range should win races. and what a great way to get it, just give the engine what it needs.

[@johnnylightning1491]

David, I work for a team in a National touring series where we are being restricted by a restrictor...errr tapered spacer under the carburetor. These are typically formerly open engines that were designed to turn in excess of 8,000 rpm. Under the restrictions we currently have the engines only turn about 6,500 rpm. Would it be worthwhile to redesign the headers to tailor them to the current rpm range? I enjoy your videos. Keep the good stuff coming.

[@jamiebowles4588]

Not David, but curious if he will agree with this: Retune the header lengths, to his unequal-length specs & targeting the reduced RPM, and you'll broaden the power band as well as enhancing peak power a bit. Mo' power off the corner. But I'm curious if his math could be more helpful on the intake side (considering the mandated restriction). How much freedom do series rules give you on intake manifold design? Surely, evening out cylinder vacuum pulses with unequal length runners would help negate the peak flow restriction of the spacer. One more thing- factor in port length, inside the head. It's not always equal, cylinder to cylinder.

[@marvingvx1]

YES DEFINITLY!

[@gordowg1wg145]

The question is, why haven't you?

[@johnnylightning1491]

@@gordowg1wg145 Because I don't own the car. I can't speak for the car owner.

[@gordowg1wg145]

@@johnnylightning1491 Sorry, I meant it as "you" meaning the team, rather than just "you" the individual. You, the team, might prefer to try the cross-over equal fire exhaust design to get a true equal scavenge affect?

[@joelamont6149]

Thank you MR. Vizard , We are building a 433 BBC in a B /Gas Belly Tank Lakester for Bonneville With a tunnel Ram / two 650 cfm 4150`s . 290 cc cast iron world heads, 714 lift int. 690 lift exh 110 lobe C/L 12:1 comp. any suggestion on 4 tube or tri Y exh, also we will be using your Pressure wave termination box because of the long tail pipes involved

[@crd-nz_001]

Ive looked into this, as this info is in the back pages of your How To Build Big Block Chevys book. But, instead of a short/long setup to get the pulses to the collector at the right time, would merging them early and running them to the collector in a larger diameter do the same job? It would look like a split. The 90 degree firing pair form one side of a 4-2-1 set up while the other 2 do the normal 4-1. Call it a 4-3-1 header. The point is to achieve the same, have the 3 pulses merge at the header at equal time intervals. Certainly not saying YOU need to try it! There are far more capable people out there than myself that could give it a go. Just adding to the thought pool to those who want to try something different.

[@WILKSVILLE]

What happened to cylinder seven on the chart at 24:20 ?

[@obbyjep7597]

I find this really interesting, thanks again dv for sharing this info

[@johnelliott7375]

God bless you and your friend Andy Wood! I have learned so much from the two of you and your my , Go to two for all of my performance and mechanical engineer needs! Great evening to you all and I hope that you have a great Tuesday.

[@corialgechrist9229]

I preach it Sir! Every engine needs a catch can and a Tesla turbine in the PCV line. Added to a cyclone intake I believe this becomes a Dual poor man's turbo.

[@jeffwooton7138]

Best information put out on YT comes from this man! Thanks DV

[@EdgarsLS]

I never really thought about this, having only worked on inline 4's I take it for granted that they have equal crank separation angles.

[@lb9gta307]

The crank seperation angles of a standard V8 is still equal, it just isn't when you look at each bank seperately.

[@brianalbrecht4423]

David the expance of your knolage is amazing....!..thanks so much 4 sharing...!...stay healthy,reguards,Brian

[@sexyfacenation]

Best old man ranting channel on KZbin for sure!

[@marvingvx1]

Hey sexy - is that good or bad - I am not sure. DV

[@sexyfacenation]

@@marvingvx1 good mate

[@BubbaAyers1969]

Sharing it out David, I’m glad you explained this Great video

[@crittercraig9445]

David Sir Thank You Very Much for sharing your knowledge with us. I really enjoyed your video and felt that you were talking straight to me and my past comments. Can you please talk a little about primary tube diameter and if they should be smaller 1.5 or bigger 1.7/8 . I will use the info in my process of getting ready to build a couple of pairs for myself. Need two pairs for small block Mopar and two sets for my slant 6s. Yes could buy if I had money but would be more satisfied doing it myself. Just like anything life brings it feels better if you can do it yourself even if it is a lot more work and time. Witch I have a lot more time than money. Hope you are enjoying a restful Sunday. Alway be safe in your travels and Take Care

[@Peter-V_00]

FWIW, I ran a stock car I built back in the 70's powered by a 327 Chevy, when I put 180* headers on it it never really came alive until I added a 4 inch spacer under the 800CFM Holley.

[@jaimedorman3175]

I recall that Mickey Thompson sold some headers (4-1) that routed the primary tubes for clearance and the length of the tubes were staggered in a long collector and the arrangement of the cloverleaf view of the primary tubes were based on the firing order. Comment David ??

[@life_of_riley88]

They were called "super scavenger" headers. The idea was to make up the primary tube length within the collector. The idea is sound, and will work, but. . .you lose the benefits of a well designed merge collector.

[@deanstevenson6527]

A minute of my time? A minute, an hour, eternity. But just not right now. Just kidding, you have my undivided attention....

[@alvarsdzenis4739]

It's funny how the thumbnail shows an engine that hasn't been used in Nascar Cup competition since the 70's. lol

[@marvingvx1]

2002 spec actually and it is my personal cup car - ex Casey Caine.

[@confuse9]

I get trying to equalize the pulses at the collector, I have talked to and read up on Herb Gebler (RIP), Jack Burns, and Ed Henneman and they are all about the signal to cylinder. Meaning, measuring how much, how long and how strong the scavaging on the cylinder. Ed Henneman is a super big fan of port matching the headers (minimizing turbulence... Allowing for smaller diameter headers etc.) It would be interesting to see what the pulses look like right out of the exhaust port vs. collector. I mean... the power is made at the cylinder...

[@marvingvx1]

The port will have a great deal of turbulence and that turbulence is present even at idle! In the next exhaust video I do I will show that, for most production engines, matching the ex header to the port is not the way to go at least that's the story according to Mr. dyno.

[@mikewillett5076]

That is interesting. What I've been wondering about when it comes to collector length is, assuming you have a 3" collector and a 2 1/2" exhaust system, would a collector extension be of any benefit even though it still necks down to 2 1/2"? (For some reason my original comments don't show on KZbin, sorry I hitchhiked off of yours)

[@duygukayhanisaskank4915]

@@marvingvx1 Hello David, The information you provide in this video is very interesting, eye-opening & throughly helpful. THANK YOU!! PLEASE tell me if unequal length headers are recommended on properly tuned flat plane crankshaft V8 engines; such as the Mustang Shelby GT350 & the new Corvette. I sincerely appreciate your attention & wait for your reply. Best regards, Ben

[@RyTrapp0]

@@mikewillett5076 For this, I would suggest watching Engine Masters on MotorTrend, they've done exactly that test - collector extensions of a variety of lengths, AND full exhaust testing, some good testing. In fact, I just got done watching the latest EM video, which was testing exhaust cutouts vs open headers & full exhaust, as well as some placement testing. The data from the EM testing alone is worth the subscription, but there's a couple good shows.

[@mikewillett5076]

@@RyTrapp0 . Oh yeah I like those guys, great videos. I haven't watched any since they charged but I think it'll be well worth it. Unless they did a video I didn't see, I haven't seen them specifically test without and with collector extensions with an exhaust system. And I haven't seen the topic anywhere on the web. I always have the odd questions. Lol

[@450ktm520]

Mr. Vizard, Gov not sure if you read the comments. For a 90 deg. Crank, 18736542. To achieve the 4-2-1... pairing would be 1,3 and 5,7 whilst 2,6 and 4,8 then add the +/- 4" Thanks

[@gothicpagan.666]

A man could spend a life time optimizing every aspect to suit every track, not just suspension but cam design and timing, intake design and exhaust manifold & system dimensions. Ah a man has, So much information, to understand it thoroughly would equally take another life time, many never would. Can't say you didn't try.

[@strydyrhellzrydyr1345]

I thought something similar...not everyone can have a set of headers.. for every optimal rpm range.. or every track... Or even every race type that he is part of... So trying to do it this way is just a bit to much.. but I do see his point

[@sbf_fox2434]

@@strydyrhellzrydyr1345 At the end there was a chart showing gains down low and up high in the RPM range and no loss in the middle.

[@hangfire6368]

I enjoyed hearing you on Real Tuners Radio a while back. Thanks for sharing your knowledge.

[@jaimedorman3175]

In the summary chart and the end of the video -- Where is cylinder 7? Hint is that cylinder 1 is called out as being both nominal and +4 inches.

[@jaimedorman3175]

As noted below by White Elemant looks like nominal are 7 & 8.

[@ericschumacher5189]

I still think there may be an error given #5 is supposed to be shortened 4-inches but it looks like the longest one in the bank from the picture of the big block Chevy he shared....

[@lousantora7238]

Appreciate you sharing your knowledge, and using it as an opportunity to raise support of St. Judes.

[@kooldoozer]

David- Could you achieve the same tuning effects of un-equal length tubes by changing the diameter of the different primary tubes? Think like, change the gas velocity to achieve the same synchronization effects as the un-equal tubes are giving you. Packaging under the hood (bonnet) might be easier. Just an idea. -----Doozer

[@Deuce1550]

I think multiple different diameters (say 3 or more) would be harder than length changes. Say 1-3/4 to 1-5/8; I imagine that'd be equivalent to an 8 inch longer pipe at a guess. More accuracy / fine tuning by length changes. Short answer: yes you could, but probably harder and not as precise.

[@robbsclassics]

If you're going that far, it would be best to figure out a shape of different diameters that would help each individual pulse from a cylinder into the collector. Even then, it would probably have to be tuned to a certain rpm.

[@kooldoozer]

@@robbsclassics The length of the collector tunes the rpm of the pulse resonance. Primary tube length (and associated diameter) relates to pulse sequencing.

[@johnelliott7375]

I would say something like that also, just listening to you every cam and head combination would be different and if you ported your parts it would change even more. Thanks for your sharing your work and knowledge with us. I will share with my friends and family. Great day to you.

[@jamiebowles4588]

I'm a pro recording musician, with a background in physics & acoustics. I've designed & tuned studio control rooms, and am familiar with standing waves, Heimholz resonators, and I played brass instruments in middle school and high school. Having said all this, I find your header solution to be quite sound, sensible, and intriguing. My head is spinning... gonna watch it again, and share with gear-head friends who also happen to be musical. Subscribing.

[@SteveSega]

I saw a video a few years ago about a Japanese mechanic who was tuning for sound rather than power. He was taking old V12 Mercedes and making them sound like F1 engines just for the comical effect of seeing people's faces as he drove by. I mention it because he was also a musician.

[@trixnhoez2964]

​@@SteveSega it's funny I just watched another video of a guy explaining engine acoustics and he mentioned equal length headers on a V12 with no mufflers will sound somewhat like an F1 car. I'd considered some equal length triple stepped headers that just hit the market for an ls1 stroked out to 383ci I'm building. Hard to know when it comes to these terms what is marketing spin and what really works best. Sounds like equal length isn't the go however which is interesting as I've seen big $$ cars make the point of saying they are running custom equal length headers like it's the be all and end all.

[@SteveSega]

@@trixnhoez2964 each cylinder needs to be treated like an individual engine. Watch the video David Vizard did on tunnel rams, and note how he had to work on each cylinder differently due to power robbing of the adjacent cylinder. If you have to cater at the intake, then you have to do the same with exhaust scavenging as well.

[@lynnrunningdeer7364]

I missed it so now it's s rerun😔. On with the show. It will be a while before my one off build but thank you for informing me my ideas is a no no🤗.

[@JACB006]

GREAT a video David …. Thank you. I have a few questions. How did you employ the TRX exhaust pressure sensor/s? Did you mount one on each primary and adjust the length to equalise the pressures? Is this optimisation possible on a V8 Tri-Y (4-2-1) setup?

[@79beans347]

I would love to build an engine and do everything that you know to do to an engine after building an engine that an average joe like me builds and seeing what the hp difference is. It would probably be a huge difference in power .

[@pauljordan4343]

There is anS.A.E.paper from the 20'sBy Arvin which you my find interesting talking about reflected waves and reversion.

[@MoparMan-ff8fb]

Hello David , Hope you are doing well . As always great video and great source of knowledge.

[@DM-ox1nj]

What's your opinion on 180° degree headers? I prefer the tone and power they generate when used with venturi collectors & used in the right application with well selected components. They work excellent on alky 377-410 sbc dirt cars. However, I would not choose them for use in Drag racing. (I remember when you & Denny from Tucson worked on project together at his machine shop)

[@TomSmith-cv8hk]

He mentioned 4 cylinders ( naturally180 degree headers) where a couple of inches from equal and optimum will lose a race.

[@remybrouwer8700]

Mr. David, you mention about the criticallity of headers on a 4Cyl engine, you have a book you cam recommend where it talks about header desings for NA 4 Cyl header designs according the flow capacity of the engine and scavenging pulses according the camshaft openning and clossing events.

[@groomlake51]

My father was one of the first 2 guys…, it’s a argument who was really first! To manufacture a 100% billet Hemi head for drag racing. True story. His shoe string budget forced him to make his own stuff on the late 70’s early 80’s. My father was a real outside the box guy that relied on fact not hearsay. I’m a FREAKING HUGE student of DV. I have grown up around and spent my whole life burning alky & Nitro in the TA/FC, A/Fuel, TAD, TF/FC, T/F category’s in the NHRA. My fathers stuff help win many championships until he was a victim of R&D aka Ripoff & Duplicate. Sadly racing drove a wedge between my father and I. I have not spoke to him in over 20 years and he is gone now. I can’t thank D.V. Enough for proving my father was correct and I was wrong. It’s flat out unbelievable how many really smart people in all forms of motor sport have misunderstood so much. Most because they over complicate and or out smart them selfs. It’s like there’s a knowledge threshold where guys and gals think they are so smart they stop listening to what the cars and engines are saying and start trying to tell it what to do. I can’t thank you enough that your so open with your knowledge unlike most all others In auto sport. I truly believe it’s the Indian not the arrow. The only person I have always wanted to prove anything to has always been my self. The only way to properly prove so to my self is to make sure it’s a level playing field. Racing proves It’s not the idea it’s the execution !

[@lawsom1]

Your summary chart at the end of the video is WRONG because you listed cylinder #1 TWICE and cylinder #7 is MISSING! Several posters mentioned this but you have not corrected it. Please do so. Although several assumed that #7 would be paired with #8 as nominal, it makes sense that #7 should be in the first group (longer by 4") since it immediately follows #5 (shorter). Inquiring minds want to know! Thanks for the fine videos!

[@richardmoerke9329]

D V how do you keep all this stuff in your head? This is going to sound crazy. On a stock motor (like a stock 340) doing all the stuff you know. On average! How much more power could you get out of the same motor? So say it got 300 hp before give it to you and you can do your stuff to it. How much more power would you get? Or is it going to be a more drive able really able thing? In any case love it and you are the man and lots to think about again.

[@chrisw8357]

Absolutely brilliant. Keep them coming.

[@worldssickestmedia2713]

I will ad this. And I'm just speaking for Street drag cars. Especially if they have turbo applications. Especially x2 if they still have fender wells. Most of these cars the headers and exhausts are built just to fit in that spot. Not for optimal horsepower. It's just a sacrifice you have to make. You have to make it like this or it's not gonna fit. It'd be crazy to dive into the math on that. How can we get optimal flow. And still get it around the steering shaft, and motor mounts, stay clear of the fender wells, firewall , down and out the back and not burn or melt anything plus get optimal power.

[@andyking9673]

during my time we used headers that were speced by NASCAR rulebook

[@mikedeal8659]

Thanks David always worth watching you.

[@CashMullen-ng4sr]

Have you ever examined the vintage Mickey Thompson Super Scavenger collector design as a simplified and clean approach from a chassis packaging perspective to optimizing primary tube lengths?

[@thomasroth4695]

Thanks so much DV. made my year😊

[@lb9gta307]

The only issue with them would be their sound. I'd imagine it'll end up sounding like a flat plane which, to me, sound absolutely awful. Great for a race car that needs the extra edge within a rule book but for something that's just supposed to be fun I'd take the hit in power for the better sound of the "incorrect" headers.

[@sandymacpherson9400]

Just looking at your chart @ 25.00 mins, what happened to cyl./port/header 7? Should that read cyls.7 & 8 nominal

[@billclark5943]

David in regard to the header principles that you are discussing should any special considerations be given to supercharged applications? On the topic of tfx I had the opportunity to use their combustion pressure analysis system about 15 years ago. I wish I would have had more time with the system but unfortunately it was only one element of a very complex project which was turbocharged big block offshore powerboat engines

[@kurtosborne9888]

Hey David (PLEASE DON'T EVER CHANGE!)...Q? If you agree and I send you a set of the set of Cadillac big block heads (WITH ALL PARTS & TOTAL-PAYMENTS!) to have porting done, when you or your associates can get around to doing it, would you post a video of the porting On the Internet? KZbin? I.e. "ONE CYL"=1 intake port & 1 exhaust port and 1 chamber. [FATFLO, .55 LIFT 2.25 INTAKE with 30°seats & 1.9 EX *it would be the 1st GOOD porting video of Cadillac heads ever posted On the Internet * it would be the 1st REAL porting video of Cadillac heads ever posted!!...I HAVE A SECOND SET, SO IF IT TAKES A LONG TIME TO GET AROUND TO THEM, I'M GOOD! {I HOPE THIS CAN HAPPEN!} Respectfully, Kurt. ps. If any cast iron fill welding on the head needs to be done I'm proficient at it.

[@woodboat3G]

i often wondered why you have equal length headers when two cylinders on same side fire back to back. It just seems wrong. Also doesn't 4 direct follow 8 so why isnt this applicable to the even side as well?

[@dmc5681]

Exhaust primary diameter is based on airflow through exhaust port on the running engine i.e. basically engine power, not air flow through exhaust port on a flow bench at 28”.

[@marvingvx1]

Agreed but airflow through the port at 28 inches is a far better gauge of what is needed if my chart sizing is followed than sizing from geometric factors.

[@bennyz1971]

Very informative video, thank you. For the exhaust pulses you showed, I think your graph was from a crossplane crankshaft? Are for the flatplane crankshaft the rules in pulses the same as for a 4 cyl engine (I think these are two 4cyl engines)?? And I wish for a video who goes deep into the secondary pipes of a 4-2-1 header. Thanks 👍🏻👍🏻

[@gk5891]

Size primaries per flow bench numbers? Same Heads: 396 that make 1.5 hp per cfm 285 cfm @ .500 496 that makes 2.3 hp per cfm. 300 cfm @ .650 How much testing of this has been done on mild engines? Personal experience leads me to believe that 2.125" would be to large in practice on that 396. The 496 seems more accurate.

[@manitoublack]

Technical Error: In the chart presented at ~26 minutes. There are two cylinder 1's. No Cylinder 7. Also was this with a conventional BBC firing order or with LS (5-7 swap) firing order? Regards Jordan

[@marvingvx1]

Regular BBC

[@larryanderson2766]

Son of A… I hit 3rd on the likes

[@deanstevenson6527]

That's because I was like 1.5. Sorry buddy. Extracted with Happiness.

[@isaacandruthruss90]

37th today. You still got the podium

[@gavinivers8941]

This backs up the reason uneven length work on the 2 litre Subaru motor in the Subaru BRZ Toyota 86GT.

[@billshiff2060]

Flow bench data on exhaust systems is an extremely crude affair. At BEST it give a very rough estimation of what is going on in a running engine. Almost none of the actual exhaust conditions are duplicated on a flow bench. Then there is the PRIMARY reason for headers and that is WAVE action which a flow bench does NOTHING to simulate.

[@marvingvx1]

Yes Bill I know what you are saying here and you are right. However the sizing method I present WORKS VERY WELL so let us not overlook that seemingly minor point!

[@billshiff2060]

@@marvingvx1 Granted , rules of thumb created by testing/experience relating cold flowbench numbers to running performance play a role in a ball park range, But the only way to REALLY know what is going on is to know the actual pressures in the running engine such as you mention at 14:00. Too bad it's so expensive.

[@johnhennery8820]

Another great video thanks again David you have nailed it 💯

[@landonthompson5604]

I also believe that Nascar has been leaving alot on the table in regards to the fundamental meaning of racing, mechanical grip has been disregarded by the money pit turd they try to polish and thats aerodynamics and downforce. I miss the old days of racing when the rules were on the engines were simple and cost less versus the money being dumped into perfecting engines that are being choked down/restricted from producing the power we once had. I would hope someday that Nascar will get back to the basics or essence of what this sport became popular.

[@isaacandruthruss90]

I have a 406 sbc in my race car. I only run it to 7000 rpm. It currently has a 180 degree cross over header setup. I need to build a new set of headers to clear my pedel box and I'd like to get a bit fancy with it. I'd like to do a true 4 into 2 into 1 system keeping it 180 degree cross over. How do I calculate primary and secondary pipe lengths and sizes?

[@adamarndt7617]

The newest version of PipeMax now will model 4:2:1 headers. Burns stainless will model your engine for 4:2:1 system if you buy your parts from them, too.

[@isaacandruthruss90]

@@adamarndt7617 outstanding, I have heard of that software but since forgotten that it exists. Thank you for your reply.

[@life_of_riley88]

@@isaacandruthruss90 Yep, get pipe max. Also search for posts on Speed Talk by Calvin Elston, or "Exhausted" as he goes over diameters a lot on there. What you'll end up with are actually 360° headers, and they'll do really really well if done correctly. They may sound a bit . .import-ish in the lower rpm range. I've built them this way and they make torque.

[@isaacandruthruss90]

@@life_of_riley88 sweet, thanks for your help

[@life_of_riley88]

@@isaacandruthruss90 Absolutely. Good luck! Building headers is a life long adventure. You never stop learning about what to do, and better ways to do it.

[@marcvan9882]

Thanks!

[@johngregory4801]

Sir, two questions... 1: On a Ford 4.6L, the firing order is 1-3-7-2-6-5-4-8. Which cylinders would need longer or shorter tubes? 2: Concerning the cylinder pulses for a V-8, using your numbering, would a tri-Y putting 1 and 5 together and 3 and 7 together, using different length tubes to make the header think it's receiving 180 degree pulses, be beneficial to bottom end and midrange? Thank you for your time.

[@williamhenk1030]

I would love to hear your thoughts on the Micky Thompson design?

[@benwhittaker8630]

When measuring pressures with the tfx gear, how is this done? Presumably you would measure pressure in each indivual runner at a fixed length, near, but before the collector, with the idea being to make adjustments to runner length that result in the pulses spaced as evenly apart as possible?

[@p0intdk]

This is a great vid DV, could you do one about turbo headers specially for straight 4-6 cyl engines. Are there anything there one should be particular about?

[@johnshackelford6965]

Well if you ignore that exhaust noise your hearing will be less until you recover after no driving of the vehicle.

[@mikemathis3936]

You have charted cylinder 1 at both nominal and at wanting 4 extra inches of length while cylnder 7 was omitted. I am thinking that one of those cylinder 1 s was meant to be charted as a cylinder 7. But I could be wrong

[@straighttimestirrups]

I think Cylinders 7 & 8 were to be the Nominal ones as he mentioned Cylinder 1 being +4 inches.

[@alejandro52612]

Great wealth of information! However what parameters would then be applicable to exhaust design for turbo engines? For example exhaust diameter vs the turbo exhaust housing diameter. Would porting the turbo housing then be beneficial?

[@justinmiles977]

Have you ever worked with a VW VR6 engine? Im curious of your thoughts about their staggered intake and exhaust port lengths.

[@blueyhis.zarsoff1147]

tfx sensor in the header pipe, I never thought of that, thats why David makes more horsepower than me.

[@zapa47]

Would 180 degree headers be better than the optimized unequal length headers?

[@marvingvx1]

No. the crossover has to be much too long for an 8500 rpm motor.

[@zapa47]

@@marvingvx1 I see. Thanks for your reply. Your channel is fantastic, by the way.

[@fivestar8337]

How many cup car headers have you built and dynoed in the last 5 years?

[@will7its]

Well if David has 4 I need at least 1.......😇

[@jeffwooton7138]

A question that comes to mind. If the exhaust is now tuned correctly, what is the net effect on the camshaft events? Seems to me, if you improve the exhaust, you can back off of the added duration that so many cams have on the exhaust side. But, DV always recommends "square" cams unless one is building a monster engine. I'm more interested in the gained torque for street and towing manners.

[@CarsandCats]

Did you mean cylinders 7 & 8 nominal? 1 is listed twice.