Big hidden HP - from anti-reversion mods
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- เผยแพร่เมื่อ 8 มิ.ย. 2024
- In this, episode 142 of PowerTec 10 DV and crew delve into the little spoken aspects of power robbing flow reversions. Follow through on this and your typical V8 could be up in both low speed torque and hi-speed power. We are talking 25-30 lbs feet and at least as much in HP.
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If I learn 1/10th of what this gentleman knows in my lifetime I will be happy.
You're spot on about the exhaust port. On our world Superbike spec engines the Akrapovic exhaust systems have this anti reversion built into the head spigots for the exhaust headers. Good stuff Dave. Thank you. We make more power on our Superbike engines usually when we flow the ports and build the floor with epoxy. We make over 225 rear wheel hp with 1000cc four cylinders turning 14-15,000 rpm
What we all need is that magic Toyota turbo inlet orifice that changes size with rpm
Amazing. What the team your talking about or if you guys have a TH-cam channel I’d love to see your superbike
Reed valves in two strokes helped.
@@cliffwright9842 Honda used reeds on 450cc single dirtbike 4 strokes too and it worked great Idle to high rpm cammed for the rpm .
@@blueyhis.zarsoff1147or just use a variable compressor?
I remember an article in Hot rod many years ago with anti reversion cones built into the header flange at the head.
It all made sense.
It's a godsend for NA engines with really wild overlap durations. Doesn't make any difference with stock timing events lowered compression and roots blowers like I run.
0 I'll😊 so@@patrickshaw8595
This reversion is more evident in larger V8's with large cam overlap. John Kasse made a point to never use old, rusty inside headers. He figured out why his friends were getting oxide in the cylinders and killing their new engines.
Tesla Valve principle I guess. Very smart application, thanks for sharing
This is why we watch your videos, thanks DV.
I've had your book on the pinto engine since I was a wee lad. I still read it from time to time and I remember the antireversion plate in that book, and also the use of the apple port on the intakes. Love your work.
I had that book too, I read it several times cover to cover. Thankyou DV for your books and your YT channel.
Same ! Got the a series one first. Both still great books. 😊
Wow, that was interesting. I had a 03 Yamaha FZ1 and had installed an Ivan's Jet Kit. Well after some playing around the bike ran well but still had a lot of pops on deceleration. In an effort to reduce this I made a cone (never heard of this before) from some steel pipe to increase back pressure and get rid of the decel pops. I installed it where the four pipes meet as one. After some playing around I had a smooth and fast running machine. More importantly, during taking it apart, adjusting (bending) and putting it back together multiple times, I had accidentally broken one of he four "leafs" of the cone. The broken, or non restricted, area ended up at the bottom of the pipe. I noticed the difference immediately. Only thing is, I had no idea what I had done. Now I know. Thanks David.
Why try to increase back pressure? That's steps taken in the wrong f direction buddy
😮
@@AshleyDonald-gr3cmlisten to the video again, you completely missed the point
@@dinadaughtry8993 read the top post. I'm not talking about the video.
Chevy 6 guys use something similar. The ports are low to the deck surface on both intake and exhaust, causing a huge flow restriction. Their solution is a "lump port" kit. These are a lump of cast iron that fits the port floor on the short side turn. This gives a larger radius to the turn. Then the roof can be ported to increase the area.
A hole is drilled through from the rocker area that does not have coolant and through the deck surface. An Allen head bolt secures the lump in place. The hole is taped with a pipe tap from the rocker side to seal the rocker area from the port.
I think most V8 heads have coolant above and below the ports, so this would not work.
This was the entire principle behind GM's "Fast Burn" SBC ports... and they were considerably effective. It allowed you to get big cam revs without excessive duration. The revised exhaust ports alone were worth 10-15hp, and gave an easy 100rpm to the sweep of most street performance cams.
David Vizard has as much knowledge I bet as anyone out there that builds engines like he has in his lifetime. Amazing man. Love for him to build me SBC for my pro 2300 lb pro street car. Thank you David for your hard work and time sharing this stuff with us.😊
I"d never even considered this before! Great information! Thank you, Sir, for sharing. Never stop learning.
I have been working on a dato head which had plates added to the floor of the exhaust. Those intake ports look too big for the valve. You can get a good size valve in if you off set the intake by 10 degrees toward the centre of the bore. I have some pics if your interested, it has 47.5mm intake valves. The engine I built is under 2l and it made 150hp at the rear wheels with the rally tires on through a straight cut gearbox! The guy who built the head it used to work with Les Collins, his name is Mark Banyard. I made a few small tweaks like individual spring seats to ensure each of the cosworth springs were nearly binding and kelford made up a special cam. It goes hard, from 4.5k rpm all the way to 9.5K and it only has a 38mm port on the intake.
I run a modified U20 with larger vavles etc, previously making 142whp before the new EFI. I think a plate system like what he describes would be easy. Would enjoy sharing info. I'm on the dyno July 9 for a final ignition map. I'm expecting 150whp and a flat torque curve coming on at about 3200rpm, 246/50 dur .530 total lift cam, 11 to 1 compression, 40mm Jenvey Heritage TBs on Microsquirt, Ford EDIS ignition, pump gas. Engine is the best ever, easy street runner with no low rpm issues. Cheers!
Excellent info. I made up some inlets many years , machined “rimflow” grooves as per Paul Ivy article in C&CConversions, and fitted them to a 649 cammed 1293. Was a lot better at idling, as you say better for getting on cam. The grooves were a little further away from the rim as I was concerned about their “mushrooming’ over. They didn't! Great memories!!!
Ditto on my 998 imp 🎉
After studying engines for years, I learned something today. Thank You! When building my street engines using cast iron exhaust manifolds I have been enlarging the top of the manifold port, creating a lip which I thought would be anti-reversionary. Turns out I should have been doing this at the bottom of the port! Mind-boggling! Thanks again, David.
R.
The location of the plate is very well explained and makes perfect sense.
I love this guy. I’ve made good power. But I wanna make all the power
I remember reading this in your book "Performance with economy" about 40 years ago!
There is no substitute for wisdom derived from successful practices. Thank you Sir.
Very Respectfully,
SKWID
Rider’s Shipmate
ET1(SS/SW/MTS) US Navy, Ret.
Killmonger: 2020 Fat Boy (Stage II+ by Blockhead)
SilverBAK: 2021 Road Glide (S&S 129ci/Fueling Race Kit by Rider’s Shipmate)
Building aerodynamic check valves in addition to the poppet valves is quite a skill.
I always love it when David says "Let me tell you a story...." lol.
It's good to hear Jim's name mentioned. He was good friends with my auto shop teacher so I got to meet him a couple times. I was just out of high school when he was working on the old quad four program. He gave a set of headers that he made to my shop teacher that he had used for testing what he called AR cone and they were used on a SBC. I do remember a small improvement in milage and not much gain was felt by the seat of the pants but the shop teacher said it was noticeable when starting to pull a hill. He made the cone the same size of the port al the way around and the expanded the tube at the cone to go around it. I'm not sure if this is coming out right cause I know what I'm thinking but not sure if that's what I'm saying. All that typed it's something I haven't thought about for along time and DV you hit it perfectly what he told me. I hear people saying stuff like we're just old school but sorry this is old news to you and me but valuable new school that work for many. PS I own Jim's old motorcycle dyno. And another PS, when I was racing stockcars I needed a crank for my mopar chrysler called a kellog crank, nobody had one and when jim found out he called Kieth Black who I believe made them and arranged for me to go to his place and pick one up the next day. So that day I sat in kieths office for 15 minutes talk about stockcar racing and left. The price...free thanks to Jim. Anyway you knocked another out of the park
Ive learned a lot in this, thank you very much
Anti reversion was one of my goals when I created step tube headers back in '83. It enables a smaller first section that boosts velocity off the port while maintaining or even increasing over all flow.
I wish David could be my grandfather, wasn't that a great lesson!
Fluidic Diode
BMW used increasing diameter steps in their headers to act as reversion dams. Since the exhaust port was the smallest diameter, the ridge from the head casting and the flange made a good dam, then the tube to the flange again had a difference in size, and each tube segment increased in size to help minimize reversion in the exhaust.
I have incorporated this technique on all of my ports since learning about it. I stopped match porting exactly on both sides and leave a directional ridge to counter reversion at each flange.
They're not "anti-reversion". They just increase the average area of the headers to increase flow. e.g. If your engine needed 1-13/16" primaries you can make the first half 1-3/4" and the second half 1-7/8".
@@chrisstavro4698 I think I will take BMW at their engineer's word when they explicitly said it was to combat reversion.
I'm not sure how they designed it exactly, but regular smooth step-up is usually used for wave tuning and to keep the speed high off the head while still flowing good. Smooth steps could potentially be less sensitive against back pressure for the same reasons, as it would have to work against higher speed and with a pressure drop moving upstream, but it's not the usual reason why it's choosen. Big abrupt steps is usually a crutch as it does a poor job in pressure recovery.
You are a great researcher David and have forgotten more than a person like me would ever have learned on this matter
I was a big fan of Jim Feulings anti-reversion seminars at the Super Flow convention I studied his video like a bible.
David, I think this is my favorite video you've done, and super well presented. It also flows nicely from previous conversations about cams with overlap impacting street manners. I wish there was a good way to characterize or score a particular cams low RPM behavior... maybe something like a surge line on a compressor map... but I'm seeing now its not all about the cam.
Thank you David. Excellent content!
1973. I built a two 8960 over and heard about some fancy new headers called anti-reversion. I believe they were built by Hooker maybe what a screamer couldn’t keep clutches or drivelines in it. Fun fun car.
Thank you so much for your time DV!
Excellent video David, the exhaust system will make or break an engine,if the exhaust port is correct you may not need a Merge collector!!
This is the wonderful stuff that's found only here. Please keep it coming. It's the reason that I signed
on for in the beginning. Many thanks.
Gday from Australia David Great video as always mate, im hooked
Outstanding video.
Amazing information.
Exellent knowledge , grumpy used to ditch cut his exhaust valves, but this looks better, many thanks!
I remember Grumpy's "Chevrolet Racing Engine"...there was a principle picture of the ditch cut exhaust valve and Vizard's Pinto engine tuning book, where was anti reversion exhaust manifold. I wonder, if the ditch cut would work better with the higher exhaust port and anti reversion exhaust manifold with low exhaust port...
You know I think I read your article because that’s where I learned about it in the 80s or early 90s but I always thought the ring would be the right way to go. This is very interesting. It changes my approach to how I wanna do it.
Thanks Much DV!!...I've been thinking about this very thing for a little while now and I'm about to fab up some exhaust gaskets for this very purpose....
Always lerning some thing new! 👍
Good. Learn how to spell 🤣
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,great to see an energizing new presentation..........,,,,gonna build some ramps in my header tubes as outlined.......
Hell yeah another performance focused video.
Think I remember this from your Ford Lima book. Great stuff.
Great video thanks
I like the information you shared with us thank you 💯💯💯💯🇺🇸🇺🇸
THANKS David....!!!!AWESOME!!!!
Muchas gracias por compartir tan buenas experiencias
Thanks, great content.
The mini’s came alive if you 8 ported the head and made manifolds to match, the alloy cross flow finally got the things working properly but the bottom end could not live with it to long. The original head design was primarily for 2nd gear take off’s and economy.
The 9 port 6 cylinder Holden engines did the same when 12 ported, the 3.3 litre (202 cu. in.)in its final form developed 330 hp with the Irving designed cross flow 12 port head, a marvel to play with.
Shot blasting ports in the reverse to flow changed drivability a lot and induced anti reversion.
Smith and Morrison’s “scientific design of intake and exhaust systems”is a good reference for harmonics of ports.
Port and manifold design and harmonics is a field that encompasses science and witchcraft in weird proportions.
People have even tried 2 stroke exhaust formulated pipes and porting (both for inlet and exhaust)for 4 strokes with variable success.
Jenkins used a reversion plate and an exhaust with short large pipe diameters and had some interesting results but not really suited to drag racing it works more for road racing where you have a large rpm range to live in.
Honda’s k750 motors had exhaust anti reversion built in with small ports dumping into large pipes, when you port matched them you lost some bottom end and the 4400 rpm hole got a lot worse due to this.
Mis matching ports by manufacturers was done for many reasons and port matching, though improving the numbers killed drivability unless you did a lot of other things to compensate.
A lot of good discussion points in this video.
Thank you David, take care.
Hey, sending greetings from Trinidad &Tobago, the part about the datsun head stirrs up memories, i had a L series engine, a N42 block and a N42 head, in the exhaust ports had a funny shaped stamped sheet metal insert, these would become loose and in some cases fall out of the cylinder head and make its way into the exhaust system...never understood its function untill now...thank you Mr. David Vizard.
Those were actually for emissions. They would get hot and help burn off any excess fuel before it got to the catalytic converter. They actually don't have any effect on port flow until you get to making some serious horsepower
thank you from david nance of alabama !!!!!!!
So cool, the Fiat multi-Air won design awards thanks to the big intake air increases.
Great info
Nice tip, i will try to aply on my little 1000cc and 1600cc turbo headers, tinking about litle inserts(flaps/cones) sanduíched btwin header and The exhaust headers
Tuliped valves probably accomplish the anti-reversion. I would suspect you could see that on the flow bench.
You are a true Master Craftsman.. and don't mind letting some secrets out..Sir you are a true gentleman..
The dynamic pressure at the reverson plate has more energy and is obstructing the reverson energy.
Thankyou Sir, This explains a lot for me as I could understand how an expansion chamber works on a 2 stroke but I never found anything relating to 4 stroke engines other than the length of header pipe. Excellent.
Thank you sir
wow. Excellent !!
Interesting,thanks for sharing.
I have my work in 2 strokes, a whole different animal.
I first saw this on a early 70's pro stock honda motorcycle based on 750 engine. They called it D-port exhaust.
This is reminding me of some 2 stroke performance concepts.
I´ve had this idea long time ago with the valveseat on intake similar to a sawtooth design. smooth going in, jagged going out.
This in the 30degree top angle.
I HAVE A 496 CHEVY BIG BLOCK in my 1978 Chevy Suburban which I built for torque and towing. I ended up using peanut port heads as they were what I could afford. A friend gave them to me, and they already had valves in them, so I was not able to port them. I then put a "peanut port manifold on with a Quadra jet carburetor and long tube headers. I am wondering if this idea of putting a dam plate in this set up would help as the headers already have a larger diameter than the exhaust port.
i remember reading about Grumpy Jenkins using larger exhaust headers to block back flow and wonder if by putting the larger headers on this engine it accomplished what you are talking about in this video.
By the way you look much better than earlier videos (I have a gap in watching your videos due to being able to get back to Thailand to be with my wife). Your skin tone and voice look and sound much improved. Keep up the health as you are one of the greatest minds in the engine building world if not the greatest.
Velocity map to the rescue....I was a little surprised at the variance found on the Datsun head.
You can get those exhaust plates for a 4v big port 351 Cleveland. but that port dives off very steeply on the floor it very well could use another angled bit welded on the end. 🧐
At that point an aftermarket 3v head works better.
Hi port conversion
@@Low760 I was referring to the tin plate you put between the header and the head it fils the the bottom of the exhaust floor in
Not the alloy block that converts them to a hi-port
Mind blown.
Thanks!
Cool, thanks
Actually carbon monoxide is flammable but gets expelled through the exhaust system, so we need to build a chamber that adds a water mist into the exhaust to seperate the carbon monoxide and feed the flammable carbon monoxide back into the intake, to burn it as a gas, which would give you more power, because fuel droplets do not burn, its the fumes from the gas that burns, so by introducing a pure flammable gas into the intake, you get a more efficient burn, with more power, so you need to focus on building a carbon monoxide extractor chamber, then you produce more power with lower emissions. 😎👍
I tried the cones,it hurt the power on my vtwin.
Great tech , going to cut that grove in my valve asap
Wow when this dude talks listen up! ✔️💯🏁🏁🏁
Thank you Mr.DV for the explanation about the anti-reversion! I wonder could a raising of port floor function as a anti-reversion plate?
I have BBF with a bad short side I thought about doing this
But I thought might be problematic
Now you are discussing it
Didn't have that on my bigo card
Very, Very interesting vid. enjoyed it. need to watch it again. does the groove cut in the top of the intake valve shorten the life of the valve seat at all?
you also have a bit in the BMC 1275 book on this i think - i seem to remember one of the UK valve manufacturers making anti reversion valves
What you're building into the exhaust is similar to a Tesla valve. 👍🏻
Knowledge = Horsepower. Horsepower = Wins!
King David Vizard:)
The Party Continues…
More High Quality Instruction:)
I believe this anti reversion will work on the old Peugeot XN1 and XN2 Engines found in the 2.0 liter Peugeots 504s and 505s I'm currently working on one and I might try this.
Haven't seen any oems do this yet except for two strokes, but I was contemplating a header with a power valve for a big port engine at some point.
I've seen some guys do antireversion seat, you could take it to the next level and make it into antireversion seat-cone.
reminds me of Leonardo da Vincy's, no moving parts, water check valve.
By adding this grove do you see any failure of the intake valve braking the outer edge off over time?
I used this tractor pulling and had no ill effects - As Long As I Didnt Cut the Valve Too Thin !!!
@bobgyetvai9444 how long did the engine last? I'm looking at street driving and high miles.
David, how are you able to observe and measure these pressure waves? Is there a way to negate or eliminate them, and if so, should you?
kind of reminding me of the flat bottom intake runners in marine applications
We did the Anti reversion exhaust trick 28 yrs ago on a bbc ski race boat. strangely the intake length had to be 34 inches or the intake charge come out of the trumpets at 4000rpm. I wish i could find the photos.
I have always made the manifold about 3 mm bigger in diameter so there is a edge around the port. I would be fun to see if that has a bit of the same effect
Hey, DV, great content. This video just read my mind, because i was googling and searching on antireversion. Couple things i would like to ask. 1st anti-reversion bottle style chamber in the runners collector, is it worth it or not. And second idea, i see some motorsport headers running bottle style antireversion chambers on each runner. But these chambers are round and antireverse top, bottom and side to side entire runner. Whats your experience on those? Also increasing diameter runners "stepped runner headers". I mean they look different to one of fixxed diameter ones, and gives of questions do they work.
14:50 short side radius...
A guy named Birdie ported my alum Edelbrock Oldsmobile heads and he even cut into the intake and had to brass sleeves for the pushrod holes. We didn't make huge flow numbers but one thing i want to point out is he kept the heads forever and kept asking me what cam im gonna run. I kept saying it will be custom based on what you can get out of the heads. We went back and forth on this for months. Then he told me the lift numbers mattereed as far as how much he was gonna roll off the short side exhaust...to reduce reversion.
Ultimately i chose a weird hyd roller from crane with LS lobes. I'll give general specs its .620/.620 lift (1.5 ratio rockers) 257/265 duration @.050 and the n/a engine made 620hp/620tq at only 6100 so in the end we did ok. Cubic inch is 462 its a .030 over 455 olds. 4.155 bore with the worst cyl head ever for actual flow. In my mind a 462 set up this way should flow more but it is what it is
@williamstamper442
The top engine guys will tell you that flow numbers do not equal power.
Lower flow can make more power.
@@bobirving6052
Yes I suppose ...lower flow numbers at max lift can have a bunch of flow below on the curve at half lift
Awesome info, thank you! How does the intake reversion play into turbo diesels? To my understanding they usually have minimal overlap.
🔔😎
Brings to mind the port plates that were used on the Cleveland heads.
Any comments about such DV ?
Intake tongues. They were wonderful items. The big speed hump on the clevos floors
Grumpy!
The 1981 Honda XR500RB 4 stroke had reed valves, stopped reversion, maybe not great for flow though.
David,
Great work. Very informative for those well versed in the more advanced aspects of flow.
Question: how do tgese principles relate to turbo charging?
The intake ridge looks good but the ramp in the header, i winder.
Have you any input ?
👍
I was told years ago if the header or manifold opening was slightly larger than the head opening it would leave a lip that would reduce reversion. So with what your saying...maybe if you only leave the lip at the bottom it might work better?
DAVID....i would call you if i had a phone. brilliant i must start a D.V. library in 24 merci