Man make these videos as long as you can. You're not wasting time, you're giving us valuable info for free. It is very appreciated.

Imho please dont apologize for the length of the video. The information you give during these videos is so valuable that it really doesnt matter how long it is if you really want to learn this stuff. Thank you and keep up the great work

I'm so glad to be a part of a generation that can learn so much without even going to school for it. Thank you for sharing your knowledge

I can't believe you don't have a ton more subs. Love your videos!

Flowbenches are to measure the difference between before and after a modification is done. the complete engine offers its own factor, like pop-up/domed pistons that get in the way of flow, bore sizes that may or may not shroud a valve (4.125" chevy small block can use the same head as a 3.87 inch bore, etc) and of course the exhaust is hotter than the intake so its going to flow a little different due to speed. But generally, a flowbench gives you an idea if your porting screwed things up or not at a "given rpm", unless you adjust for revision at low and high engine speeds from piston pumping (for those doing the home vacuum cleaner method by David Vizard back in the day, remember it doesn't have to be accurate to other machines so much as it has to read consistantly every time you test the same parameters) What's nice about getting the right valve angle cut for low to mid lift, is it acts like an overlap condition in the cam, without having it ground in and the resulting issues.

I got a lot of my schooling paid for and still spent over $30k. You are giving this info out for free. If people complain they can go and pay 10's of thousands of dollars for information from an instructor that does not even put to practice what they "teach". You are showing real world information and not charging us? How can people complain??????? Thank you very much for the info

Good info! The way I think about reversion and e haust flow, is the air column is like a spring. When the compression is released, it expands and then contracts. The frequency is controlled by the length of the header, and the energy of the "air spring" is controlled by the diameter of the primary pipe. If the energy is strong and the frequency matches what is needed for the desired rpm, good things happen!

I am only 9mins in, but I can tell you I am hooked because I love this stuff! Extremely informational, you are doing an excellent job explaining things. 👏 I would totally pay you for consultation or even classes

Every day is a school day. While the amount and value of learning is up to the student. The content of the lesson is wholly of the teacher. Eric, your content is wholly awesome and great value. Thank you Only if I could find someone into smaller engines (bikes) with teachings on your level!

With 395 likes and only 6 dislikes, I would say your presentation was near perfect. I'm a beginner and I understood you and learned a ton. Thanks.

I've really been enjoying your videos. Lots of good facts based information.Thank you.

This was really interesting to see. About the shape of the exhaust valve, I'd like to see you making video with valve that has been smoothed on the cylinder side of the valve, chamfer or rounded bottom of the valve. Compared to regular

I appreciate your lessons in porting and evaluating your work and others as well. Sometimes I can see for some it might be a little hard and not get confused. Not to worry as we will find out eventually learn what people with fantastic experience. Especially when it doesn't cost anyone. My next set of heads will be prepared be you. Thanks for all the detailed work you do

This was an excellent video. Thanks for the detail, you conveyed a lot of information. Thanks.

Thanks Eric. Just a brief understanding of physics agrees with flow overlap and reversion. explanations you are showing helps with tuning an exhaust system

Great job what a class you always clear up some misunderstood area.

Exhaust flow pipes have been beneficial when testing 55 to 58 degree seat angles at elevated test pressures. The prevention of shearing at the exhaust flange allows you to see the effects of smaller seat geometry changes. A final flow testing with an intake manifold, carburetor and header tube (or flow pipe) will give a more realistic exhaust to intake ratio; which some people overly obsess over.

Hello to my fellow Oklahoman. Glad your Tube came across. I am a student of Engine Behavior and modifications. Working several projects. Learning from the Best. One thing to keep in mind, length of string of info is easy here. We push pause all the time. Life gets in the way of acquired knowledge. And some Sponges take it slower, Some fast. And then there is Bounty, quicker picker-upper. You do a great job. I am an A/P, Machinist and Antique Car Restorer. @-67 retired. Appreciate your Hard Work.

Thanks for going to all the effort in making this video! You have a passion for this and it is entertaining and educational. Keep up the great work!. I love the longer video! More tech the better! Thanks mate you are a champion!

Excellent and very well explained tutorial. It was nice to see somebody talking about reversion and actually showing the different valves. Not many people will do that if it all anybody. And educational video can never be too long as long as you keep the information flowing and informative. Just my two cents worth

Thanks for the knowledgeable demonstration you know back when I bought camshafts you bought one and hope you got the right one and I got screwed because they changed the cam to a different box and I didn't know it so I had a 327 with a huge camshaft

Hey eric, great video and don’t ever apologize. You are taking your time to do this and show all of us real live tests with real world results, not to many others doing that. It kind of falls under the “ My shop my rules “ thing. I really like how you make a statement and then back it up with test results and show why. I would like to send a set of BBC brodix heads I have that need going over. Thanks again Eddie wheels 🧑🏻‍🦽😬👍.

Thanks Eric!!... Thats really good info!!.. Wasn't tooo long for me!!..

I love this channel, appreciate the info.

Great and very informative…your testing is very comprehensive and easy to absorb….I would like your cam recommendation

Extremely interesting information, thank you!!

Great information i appreciate it.

Very good information and explanation is great😊

This is awesome info! without spending any money going to any High Performance schools……keep on doing this and thank you for this!!

Thanks a lot for the sharing your knowledge one of the best videos on KZfaq.

Top Notch Sir, God bless you.

Nice talk about the cam guys! Experience not only in the timing events but valvetrain motion and stability is paramount. Kip (Cam Motion) and Tim (Bullet Cams) is who has done 90% of my grinds. Tooley has done a couple as well, usually with either Comp; Bullet or Cam Motion lobes. Great Vid! Keep em coming! We've lost a couple of the original "Cam-Fathers" in recent years with the passing of Harold Brookshire and Harvey Crane. It's amazing to see what their pupils have done adding modern technology to their old principals!

Now do a flow test with a Performer RPM dual plane, And a Single Plane, and a Tunnel Ram intake test with the same head.

Great insight THANKS

Also, very nice to hear you recommend Mike Jones, just bought a solid roller and lifters from him.

Great info and I totally agree with you.

Great video and I will try some of those tests on my flow bench!!!

I discovered your videos about a month ago. I've done some minor port jobs myself with my own engines and made some decent gains (proven on a dyno, back to back with a stock unported head), and even though I understand the more basic principles of porting, I've picked up quite a bit of good info from your channel and learned some dos and don'ts in case I get into other projects. Your videos are plenty thorough and you do a damn good job with explaining the theories behind all of it. Keep up the work man. Awesome videos.

Look at exhaust headers for 4 stroke dirt bikes. It helps to increase low pressure at specific rpm to improve scavenging. Similar to what an expansion chamber does for a 2 stroke.

So I was just thinking about reversion and I work on bmw's and the n63 I have had the exhaust off of many times. The tops of the cylinder head ports are about 1/16 smaller then the manifolds. I think this is built in anti reversion, but I'd be interested in an experiment ether making a knife edge version with a solid block on the manifold side and seeing how that flows both ways and intake side finding the highest flow points which are probably different depending on which way the air flows and blocking the reverse flow a bit and see how that performs. The exhaust would also be interesting to angle the port up a bit more at the outlet then dimple it. Air going out would lose a bit, but reversion the air would run into that angle air foil which would slow it down. Idk could be interesting to see

Excellent info Eric. Thank you

Man thank for all gold you give for free is real apriciated

That was a fantastic video. I learned so much. Thank you very much and have a nice day.

Thank you for your great advice!

Eric I give you all my respect and thanks but I think you should just stop worrying about some the stupid comments and just do what you want to do. It's your channel and if someone doesn't like the way you do things that's their problem. You obviously don't just do these kind of videos for fun so people complaining about little things like " why don't you measure every little increment in between what you did" I understand some deserve an answer but I think you've answered that question a few times now and I cannot stand hearing broken records lol. I see what you're saying about exhaust on flow bench. It's like just stating "OUR HEADS FLOW 300+ CFM" then in fine print it says *please note heads only flow 300+ cfm past 1 inch of lift* bad marketing for the consumer, good for the producer.

Your scientific data driven approach is the best on KZfaq

The Intake Valve open's while the Piston is still in it's Exhaust Stroke because the evacuating Exhaust Gas's create a Negative Vacuum that help's Draw the A/F Mixture into the Combustion Chamber. It's called Overlap.

This is the stuff I love to see!

Any time you change air flow direction its like creating a restriction, bends curves ect. Up and away is best when possible.

Great info and well explained sir' thank you for sharing

Very easy to understand, thank you sir... subbed'

Thanks for the info man👍

Question , did the flow increase when the pipe was turned upwards because the SBC exhaust port exits upwards? Factory SBC rams horn manifolds exit up before they turn down wards. Was just wondering.

Great video, learnt a lot from this , BTW the longer the better !!!

So, if I understand you correctly, once you get above fairly low RPM's the tulip shaped exhaust valves with a 45 degree angle and no backcut flow the best. Is that correct, and, if so, Is the same true for intake valves? Thanks!

can you use set up cam timing so that the negative pressure created by combustion aids in port velocity and negate some of the effects of having heavily ported heads?

Eric what about opening exhaust valve early? Using the blowdown phase..

Thank you for taking your time to share your knowledge with us.If you to take the time to teach I will take the time to listen and hopefully learn.

Do you ever flow the heads with them fitted to a block with pistons fitted, and test the flow to the timed valves to piston to see what turbulence effects take place?

hi thank for your videos you have some good info so thank you for all your work..however i do have question with this video regarding the exhaust flow test "Out then In" ( reversion ) i understand what you are saying it makes sense but overall if we solely judge off the middle valve numbers with the back cut the only negative is .100 lift..which would be a 0.8 loss if you go to 2.00 its 6.5 gain, 3.00 is a 5.4 gain, 4.00 is a 19.3 gain, 5.00 is a 36.6 gain, .600 is a 46.4 gain and finally .700 is a 55.3 gain- total = 169.5 so even though yes that valve has the most reversion it still beats out every other reversion number after 1.00 lift, reversion is a result of an event in the combustion chamber correct? explosion then reversion, but the flow number going out of the exhaust still far exceed the reversion numbers so surely it IS better to have a back cut on the exhaust valve??? the standard valve has the least reversion but it also have the worst exit flow. what do you reckon?

Excellent info. Keep it coming. You explain it well. You were a teacher after all. I think on that particular cylinder head you can gain more exhaust flow by unshrouding the valve on the quench pad side.

Eric I love your channel. Proper in depth information and explanation of what is going on in the head and how to improve it. Brilliant stuff! I watch Holdener and Vizard too. It's great that you guys with such great knowledge are sharing it with us on KZfaq.

Sounds interesting

In one of your video's you me mentioned over scavenging can hurt power. I wanted to put just a bigger exhaust valve in my peanut port heads (226/156 cfm intake and exhaust) on a big block chevy, but after watching whatever video that was I was wondering if that would help or hurt power now. Do you know if over scavenging a risk on a head like this? You're probably thinking it isn't worth putting any money into them, but I thought it would be fun to see what I could get out of them power wise.

Hey Eric, how about a follow-up where you go down the rabbit hole If there's stuff I don't understand in it, I can always ask questions or, God forbid, actually study until I do understand ;-)

Cool, now I'm even more confused about tube header size!! ha ha ha I guess like everything else, you're going to need 5 different sets of headers and time to test, test, test, to determine which is best for your setup!

If you run stahl header flanges, does the flange need to match the exhaust port exactly? Or as long as the flange port is bigger than the head exhaust port it is fine?

The term I use to describe it is "the scavenging effect" Love your channel BTW...

Hey, i have a 04 bmw lk1200 horizontal inline 4 im building for higher flow but im poor and cant afford cams, but i know i can adjust duration. Im going for e85 and rc fuel spayed at the top end. I want high rpm can you tell me from stock cam spec how i show split the duration between intake and exhaust cams compared tl standard, or leave it alone or move intake one tooth forward only ect? .. just wondering and if you find the actual cam specs i would love them and what you recommend. Making it into a turbo gokart/buggy

Could you do a test on header flange to head flow ? You see some flanges mostly sbf overlapping the exhaust ports from oval port header flange to square port . In some forums I have read most of the flow travels through the middle of the port that and doesn’t make much of a difference. . Would be nice to know if its true or not .

Did pipe up flow better due to it being the same direction as the port?

Great explanation of the “5th cycle” of overlap cams. The smog cams in modern engines don’t utilize it which is why an aftermarket cam can outdo a factory cam across the rpm range. Great video!

It seems like it would be worth flowing your exhaust ports with the header you are going to use. It may even be worth shaping each port differently. I know some guys that have 8 different profiles on the same cam. It seems like those guys never want to share information about it.

Darin Morgan mentioned using an air tanked pressurized to 500 to 1,000 lbs, put a stop on the valve stem then whack it open with a hammer then measure the pressure drop in the air tank😅

This is great, Eric. Question - You have probably said this many times before, and I know you have mentioned the challenges, but can you explain why the engineers designed the head with the center to cylinders having the exhaust port together? The valve pattern as we see it in this video is - EI IE EI IE where E-Exhaust, I-Intake and not alternating EI EI EI EI Thanks!

About 4:30, absolutely, a running engine pulls more vacuum than a engine just spinning over, and rpm has nothing to do with it. It's the exhaust pulling thru the intake, the exhaust has a large effect on the intake!

I know this is a older video and it's actually the second time I have watched it but I had a question about valve size. Basically how does the diameter effect the reversion. Lets say it was a smaller valve. Would you still prefer no back cut tulip style.

Thanks!! GREAT JOB..GREAT INFO!!

What about the hemi eagle head would it help to back cut

While watching the video started thinking about how engine power seems to be affected when you get a gasket leak at the header flange and or how engines respond off idle so much faster when they are on un-capped headers and the video somehow provided some insight into these dynamics and the importance of "controlling the variables" to avoid unfavorable tolerance stack up. Would be interesting to see some engine dyno data show how much power is affected when varying intake vacuum leaks then exhaust leaks are created on just one cylinder. Thanks for your time....and that scene from heat is one of the best...

Hello what do think of the desk top computer dyno

Thumbs up.... Great content! Thx!

awesome info, you just got another subsciber.many thanks.great job

Have you ever flowed the exhaust port where the port exit (header side) was attached to the flow bench?

Thanks!

Can the flow bench flow in both directions? IE pull air in for the intake and push air out for the exhaust or does it only pull air in through both ports?

You might find this interesting about marine inboard and stern drive engines. A few years ago in one of my Mercruiser recert classes they had one of the training engines set up as usual in a test tank but also had clear exhaust pipes coming off of the exhaust elbows. Marine engines with a few exceptions discharge their cooling water through the exhaust after the riser which for the most part prevents water flowing back to the engine cylinders. When throttle was opened to about half and closed suddenly, the reversion could be seen in the exhaust by the water trying to reverse towards the engine. The exhaust pipes where on a downward slope about 30 deg. but the water would still climb backwards. The marine cams on non performance engines are something similar to truck or RV cams. Nothing exotic.

Been watching a few of your videos since the almighty algorithm recommended you and I've been seriously impressed with your knowledge and your ability to convey complicated ideas in a simple fashion. But what tells me you're a guy who really knows his stuff is the fact you have a Harbor Freight toolbox right next to an expensive flowbench. Put the money where it counts, not on flashy accessories.

...curious.. very many variables, blend that header and port match .

Thanks for the video!

Thanks for video!

Applied to stepped header design?

Brilliant, sir. Simply brilliant. If your ears are able to detect sound differences between valves, why not quantify the valve acoustically and see what that says? Has it ever been done?

28" vs 8# how dose flow change ?

Any chance you could shed some light on what size header tubes to use for different power levels?

Tanks...

Awsome content

Good stuff

Quick question, would Porting a Carbureted Motorcycle Head require a Jet increase?

Like a machine gun, gas's kick out the spent round and spring assist reloads the next round. Air flow in a engine vs air flow in a gun ... Similar??