Anti-Reversion Headers

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Re: Anti-Reversion Headers

Post by BAracer » Mon May 21, 2012 6:13 pm

Hey Larry, is that an early Weisman transmission? The shift turret system looks similar, and they were a high-end builder during the 60's

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Re: Anti-Reversion Headers

Post by pheyden » Fri Oct 12, 2012 8:24 am

Weisman still is a high-end transmission manufacturer. Located Costa Mesa CA and still going strong as far as I know. Most off-shore boat gearboxes these days. Most people do not remember that Weisman was the first to use the "quickshift" principle. Quite unique and used in almost all F1 gearboxes these days.

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Re: Anti-Reversion Headers

Post by user-9613590 » Fri Oct 12, 2012 2:35 pm

Larry waiting someones heads for his project :shock: :?:
Well,even if you are good at something but just admit that someone makes really good stuff why not.Buy his heads.Why spend lot of time and money when you can get tried and tested.

It just at first looks funny that old pro waits his heads done.. :lol:

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Re: Anti-Reversion Headers

Post by Fendermate » Tue Jun 09, 2015 1:46 am

It's been years thinking anti-reversion was dead until I saw this thread. In 1979 I came up with the idea, built some headers and tested it. Next was trying to patent it. At the time, here in Canada, you couldn't patent an idea. The patent application was to protect yourself for one year while you set up production and distribution. So, since I didn't have the $1Mil. to set up production, I tried selling the concept to header companies I was dealing with; Hooker, Doug Thorley, Castler, Cyclone and Hedman. No one was interested.
6 months later, my wife comes running into the room crying and showed me a CarCraft magazine and on the cover page was; Hedman AR-1; revolutionary headers. You can imagine what was going through my mind. So, I went through the article, saw their test results and realized that they got it wrong. Well, I didn't give them everything in my original letter and, of course a phone call was in order. They said someone else within Hedman had came up with the idea before me and there was nothing to be done about it. I knew it was going to happen anyway so why push it. They did send me a free set of AR-1 headers. For what reason, I don't know.
The performance improvements they achieved was impressive enough where I naturally assumed they would be reverse engineering it to find out why it worked and then be able to apply the technology to any 4 stroke; stock, street performance and a variety of racing applications.
They didn't. So, it died.
Through the miracle of the internet, I see it really hasn't died and that makes me happy. But, what's interesting is that after all these years no one still really knows why it works.
The principles should be part of every production vehicle by now.
30 to 33% increase in volumetric efficiency is just the start.
I took a 1974 Chevrolet Camaro Z28 that had the worst fuel economy in the history of Chevrolet (18 mpg and that's imperial Canadian gallons) with a stock weight of 3240 lbs. 3 spd auto and 3:23 non- posi- track and went to work.
I did a full 'frame off' rebuild to make it dependable for the test I was to do. The transmission just got the shift points strengthened and modified and the unibody strengthened but left stock.
The engine got fully blueprinted and balanced, heads remained the stock 194 skinny castings other than the A/R process applied to them, 9.5:1 cast pistons a good chain with a Comp cam 268H and to top it off was an Edlebrock dual plane Performer manifold. The carb was the stock 4MV quadrajet I massaged to about 700 cfm but kept the stock jets and rods to start, then off to the dyno for engine testing. t
I tested with exhaust manifolds and 8ft. of exhaust pipes (to simulate real world), Street headers with 8ft- 2 1/4 pipe, the Hedman AR-1's with the same exhaustr and my A/R's, with tri-y collectors and the 2 1/4 exhaust.
Manifolds and street headers gave us numbers we were expecting; basically the same torque curve peaking at 260 ft lbs but at different ranges.
The AR-1's gave a boost to the low end, improved the mid range but topped out about the same as the street headers. The torque curve was flatter but not as impressive as the advertised numbers were. Probably because they chose to use 1-1/2 primary tubes, not the 1 5/8 as the street headers.
My combo produced 300 ft lbs at 1400 rpm and stayed there to 6200 rpm. on the first set of tests
We tested for three days with the same torque curve results but increased it to 320 ft lbs by reducing the jetting from 72 to 68 primaries. With the car put together, still at 3240 lbs, we took it to the local drag strip and best out of three passes was 13.2 sec @ 110 mph (could have used some tires for grip). Then, on to the fuel mileage test and over two days, with no changes was 29.2 mpg.
Over the next few months I tested the process on a Briggs and Stratton 5 horse rotor tiller and turned it into a stump puller and a mud racer producing some serious power. That was fascinating!!!
When it came into the shop, idle speed was about 2500 rpm just like a pro stock. With just the exhaust change (A/R's designed for that combo) I turned the idle down to 850 rpm and smoooooth.
Yes, the owner was disappointed because it didn't sound like a race car anymore, but I warned him of the additional torque and more top end. He didn't do his test runs to find out and wrecked. (tore the paddles right off the rims.) He was beaten up but okay and came back wanting more...crazy bugger!
Sorry to reminisce but these are good memories.
There are other serious benefits like little to no NOX production, but that's for another discussion.
I'm dying to play again.

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Re: Anti-Reversion Headers

Post by modok » Tue Jun 09, 2015 3:19 am

Wow, I'd love to hear what you came up with. Did you know the same thing happened with CDI? The Americans stole that from the north also.

I do remember how the Vizard AR headers were made.
If you want to discuss what they do, IMO, there are several different changes happening at the same time.

-- physically resisting reverse flow

--eliminating(or reducing) pressure recovery from the port size(valve choke size) to the header tube size

--adding volume to the head end of the header.

Now, if you don't mind, for now assume the port is about 85% of valve size, and the header ID is about 100% of valve size. Why that is....is another subject, for now for the love of god accept it or I'll get nowhere. LOL

How should the port expand to the header? David V.'s earlier book advocated a tapered exhaust port. I think this was because it works good on the flowbench.
On the engine, tapering the port to the header is something you see rarely anymore. Not that nobody tried it. Everybody tried it, and, like an open megaphone it certainly DOES DO something, but usually just peaky as all hell, and just too extreme to make use of.

Pressure recovery is a buzz word these days and THAT is what a taper will do. If you put a length of header pipe on any engine, it will act like an organ pipe, and I'll also assume you know what that means, and also have simple ram from momentum.
The taper, recovering pressure, means that the header will be "able" to pull the cylinder to a lower pressure than the pressure in the header to some degree while port flow is fast.
Initial flow into the header tube makes pressure, then the gas in the tube gets going and has momentum, if the rate of flow into the header slows down it will begin to pull vac by simple momentum even without wave tuning. If it starts pulling vac it may run out gas to flow.....which means, there can be a point where flow is STOPPED, or so slow it mas as well be. If flow is stopped, and the pressure in the cylinder is lower than a few inches into the header...........it will start flowing backwards QUICK. So there will be a quick pressure spike at that instant. The taper can encourage the header to "out pace" the piston, and run out of gas to flow, and then velocity stalls. This will always happen to some degree, but realize that the pressure recovery certainly does INTENSIFY the stall. A taper does NOT aid flow in blowdown condition. In blowdown MCSA is the only real thing controlling flow IMO. The header tube does not need pressure recovery to work either, only momentum and wave tuning. It could be that to tune for a broad range, a port that flows well at highlift/blowdown but worse at flowbench testing pressures may will extend the rpm range. Idea being as rpms go up, and blowdown is extending later into the stroke the port can keep up, and header still pull vac when flow slows at tdc, because it by logic MUST slow when there is no more gas TO flow. and you want that be because the piston stopped at TDC, not because the header vacuumed out all the gas prematurely by "out running" the piston.


My take on this: pressure recovery from port to header=bad Now, I don't think there is only one right way to do that. There are probably several. But you sure as heck don't taper an exhaust port if you want any kind of broad range power on a four stroke. That doesn't mean stepped headers are OUT. The taper in a stepped header is so gradual it is different than a port and a header with a venturi tail connecting them.

So, i look at a little D port and a big header tube and I see the opposite of a venturi. Others may see a physical one way flow device, but I don't.
And David V. might have been promoting the solution for the problem he caused with his tapered ports. I wonder what he has to say these days?

So how do you test an exhaust port?? Even a stub does recover some pressure. As you might note testing an orifice right on the bench verses on top a cylinder.
Maybe go ahead and put a megaphone on it! WOW FLOWS A LOT MORE. But your testing pressure is not what it says. Test the pressure in the megaphone and you'll see that with the megaphone you are testing the PORT at a higher differential, which can be measured and corrected for. All you did is make the bench more powerful and efficient. So, yes to megaphones: they save on electricity. I've heard guys port exhaust ports for highest exit velocity, and that's actually the same thing. One guy said he ports for exit velocity says he likes to taper the port out. Right then I know he's drinking the coolaid but not taking the trip. LOL

Now, the "one way" idea, and adding volume to the end, those also are real things. But I'm out of breath for now.





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Re: Anti-Reversion Headers

Post by hoffman900 » Tue Jun 09, 2015 5:50 pm

Here is a photo of a buddy of mine's 289 Cobra circa 1969 and 1970. Note the exhaust. This set-up was worth 30hp over the side pipes that Holman and Moody built for these cars. An engineer friend and the driver/car owner / builder developed what you see here. It was the fastest 289 Cobra in the country circa 1969 and 1970 (lap records, divisional championships) and finished 2nd in the National Championship in 1970 to a newer, pseudo factory backed '69 Corvette

Image
Image

At the time, they were also fans of the step at the exhaust port, but obviously, things have come a bit of the ways since then. For fans of history, the head also had stock heads ported by AFR (the original AFR - also had to use stock valve sizes per rules), worked with Harvey Crane on a camshaft, had to use the stock manifold and carburetor, but were able to mix and match Holley parts to come up with something that worked a little better. Made ~350bhp.
-Bob

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Re: Anti-Reversion Headers

Post by Fendermate » Wed Jun 10, 2015 1:38 am

There are so many ideas out there on how to massage exhaust to squeeze every ounce of power you can get. Anti-reversion is the most basic and also the most misunderstood. So, let me put a few things as straight forward as possible so it makes common sense.
1-- A pipe has to fill up before it starts flowing. Once it does flow, it takes energy to stop it. So, when designing exhaust systems, bigger is not better. It has to be matched to your engine package and the rpm range you want it to work in. A common mistake is thinking that a 4 in. pipe has double the capacity of a 2 in pipe. In reality it's close to 4 times the capacity.
2- Because of valve overlap, at the end of the exhaust stroke, the intake valve is opening and exposing pressured exhaust to manifold vacuum and naturally a vacuum needs to be filled. This is called REVERSION. The bigger the cam lobe duration, the more exhaust is sucked back. At minimal, it will try to re-enter the cylinder and at worse, it will also enter the intake runner. (See any black carbon on the intake runners?)
3- Reversion is a built in EGR valve. If 10% of the exhaust is allowed, it will contaminate an equal portion of 10% of the fresh air/fuel mixture and that means 20% of the charge will not fire.
4- Historically, a 4 stroke, naturally aspired engine, no matter how you massaged it, had a 4,000 useable rpm range (if you matched things right). You could move it around but couldn't stretch it because anything above or below was weak.
Now, there's been a lot of science trying to work around these 4 realities; 4 valves per cylinder, variable valve timing, using roller systems so that radical cam profiles can be used and keep overlap to a minimal.
Here's a side note; When Competition Cams hit the market in the 70's, their business hinged on acquiring a patent that had expired from the 40's. That was an asymmetrical shaped lobe for quick opening and slow closing. It gave the same lift and duration as other competitors but having .050 lift much earlier really got the power started. You ask the Comp Cam rep about it today and they'll say "What???"

So, what does an anti-reversion valve do?
It is simply a one way resistor to delay the reversion effect and give time for the exhaust valve to close.
How does it work?
Since hot exhaust wants to expand, we give it the opportunity to, but only in the reverse direction.
anti_reversion.jpg
Where to put it?
At the tail end of the largest pulse of exhaust, where the exhaust slows down. If your header is port matched, it is approximately 7-8 inches from the header flange. To be more accurate, you can map out the temperatures of the header pipe and there will be a temperature spike where the exhaust slows down. This spot will have the greatest affect. This spot is relative to engine displacement and not rpm. So, moving it higher or lower just makes it less affective.
That's it for today.
There's still a lot more to talk about.
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Re: Anti-Reversion Headers

Post by modok » Wed Jun 10, 2015 3:06 am

Very interesting. That is quite different than the "ar" headers with a small cone inside at the header flange. When I made some AR headers, I did it right at the flange too.

When I read past "tail of the pulse".........it caused a slight twitch in my left eye. Recalling all the times I've heard some guy explain how a header works involving the tails of pulses. Which, fortunately, I didn't hear repeatedly until well after reading Philip H smith's book, and then stealing it from the library, and reading it again, a few times.
Much like the book, after making a cup of tea, and reading it again, actually I don't see a problem with that phrase. If the pulse is as long as the header, then 8" in would surely be right on the tail of it.

The idea that the hottest point of the pipe is a point of interest, that does something.......there may BE something TO that. Certainly.
I've seen strange things happen from messing with the header in that area and don't know why.
AND, I've never paid attention to where the hottest point is.
I'd expect to learn nothing more than the bends are hotter, but maybe not. Usually what I expect is happening, isn't; that's the scientific method!

Ever seen a "singing pipe"? You put a blowtorch on one end of a closed pipe and it starts singing.
I've wondered if headers have a similar thing going on.
Glen Urban

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Re: Anti-Reversion Headers

Post by BlackoutSteve » Wed Jun 10, 2015 7:00 pm

Is this the Vizard AR cone that is being discussed here?

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Post pictures, or it didn't happen!

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Re: Anti-Reversion Headers

Post by modok » Wed Jun 10, 2015 8:47 pm

The earliest mention I recall, in the 70's? Vizard tested AR headers with a small cone inside right at the header flange, they probably were cyclone brand.

Your illustration does not show it near the head, and there is no cone shape, so I think that counts as a different concept.
The guy has done a huge amount of testing work, I would not be surprised if he has tried the other concept of having them further down the pipe, but I'm not aware of it.
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Re: Anti-Reversion Headers

Post by MadBill » Wed Jun 10, 2015 10:44 pm

The above pic looks just like the 'aneurysms' that Jim Feuling used in the header primaries of the closed-course record setting Oldsmobile Quad Four ~ 30 years back...
Felix, qui potuit rerum cognscere causas.

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Re: Anti-Reversion Headers

Post by dirtracr5 » Wed Jun 10, 2015 11:05 pm

If anybody is looking for some here they are.
http://www.speedwaymotors.com/Dynatecha ... aQodXkEAqw

They worked very well on our 2bbl motors. They are not legal now for us.

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Re: Anti-Reversion Headers

Post by CarterHendricks » Thu Jun 11, 2015 12:36 am

BlackoutSteve wrote:Is this the Vizard AR cone that is being discussed here?

Image
That is one of the drawings from Feuling's patent.

http://www.google.com/patents/US6336471

Here are some photos showing fabrication:

http://www.realhomemadeturbo.com/forum/ ... ic=13772.0

--Carter

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Re: Anti-Reversion Headers

Post by Fendermate » Thu Jun 11, 2015 1:19 am

Wow!
It's great to hear others were testing this. But I'm also disappointed in myself for not being able to continue at that time and not having the resources to fight for it.
Modok; you said Vizard tested AR headers and you thought they were Cyclone brand. When I mentioned this resurgence of interest in AR, my wife also thought it was Cyclone that grabbed my idea. I still have all the info filed somewhere. You may be right and if so, I stand corrected. The time frame is right but the name Vizard never came into the picture.
When I said "They got it wrong", I meant the placement of the valve.
For the valve to function as a resistor, it needs expanding gases. If you think of the exhaust pulse shaped like a teardrop, placing the valve where the highest volume starts to taper off makes sense because the highest volume is also being constricted within a small diameter. The expansion area of the valve gets filled on the reverse flow easily and the result is that the exhaust mass itself becomes the resistor, maybe for just for a millisecond, but that's all that's needed. Placing the valve at the flange isn't a premium spot because the reverse flow has already built some momentum and, as we know, would take more energy or a larger resistor to stop it. In addition, because of the flange mounting bolts being so close to the port, the AR valve would have to be physically smaller in capacity.
I also said at the beginning that I had thought that the company that took the idea would continue testing to find out why, specifically, it worked and would continue refining the product and if so, would discover the chain reaction of benefits I discovered related to the Anti-Reversion process.
To date I have only seen the exhaust side being played with.
So, maybe there's hope for me yet.
Carter; I just got your post showing the patent as recent as 1995. Boy, do I feel like a schmuck. But, then again, I tried patenting it here in Canada and they wouldn't go for it. Sometimes I really hate our backwards bureaucracy.
Maybe we should get Fueling involved with this discussion too. He may have continued the experiment.

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Re: Anti-Reversion Headers

Post by Leftcoaster » Thu Jun 11, 2015 2:09 am

Jim Feuling (note spelling) died in Dec 2002, reputedly of cancer

He held many patents and was a true innovator

Larry Widmer's forth and following posts on pg 1 gives an example of what has worked for his 4cyl 4v Honda engines

Note his statement that the anti reversion chambers needed to be within 12" of the flange, and was complemented by an exhaust port smaller than the header primary

Check http://www.hytechexhaust.com for information on the anti reversion chambers they supplied to Widmer, and other products

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