Anti-Reversion Headers

General engine tech -- Drag Racing to Circle Track

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joe 90
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Re: Anti-Reversion Headers

Post by joe 90 » Tue Oct 10, 2017 5:27 pm

I think the biggest difference with his idea is that it was really meant for water, incompressible flow.
With gas (compressible flow), as you say, you want the "valves" to be as close to the source as possible to get the maximum effect.


Looking at his patent , I'm sure it would work for exhaust but would be quite difficult to make.
Maybe good to experiment with a lawnmower?
Although these days just make it with 2 flat sides and a middle divider (valve section) laser cut. Bolt the 3 parts together.

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Re: Anti-Reversion Headers

Post by digger » Tue Oct 10, 2017 5:53 pm

That looks like if would offer fairly high losses, what is to say that a straight pipe of small diameter offering the same back pressure doesn't produce superior area under the curve ? Looks like it might be difficult to adapt to a round pipe

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Re: Anti-Reversion Headers

Post by psychomotors » Tue Oct 10, 2017 8:25 pm

Geez I'm glad this old thread was found. I have been interested in the AR stuff ever since reading about it in one of DV's books a year or so ago. Always wondered why it fell away.
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Re: Anti-Reversion Headers

Post by sanfordandson » Tue Oct 10, 2017 9:14 pm

We have found good gains with A/R "mufflers" on our circle track engines. Specifically bottom end torque.

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Re: Anti-Reversion Headers

Post by digger » Wed Oct 11, 2017 3:43 am

its interesting about the ideal location for an AR device we have heard at the valve or close to it ? is it correct? or does putting it in the high speed area induce higher losses? i have read exhausted's take on it (i.e. not at head/flange)

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Re: Anti-Reversion Headers

Post by va454ss » Sat Oct 14, 2017 2:14 pm

sanfordandson wrote:
Tue Oct 10, 2017 9:14 pm
We have found good gains with A/R "mufflers" on our circle track engines. Specifically bottom end torque.
Are your gains with a standard collector?

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Re: Anti-Reversion Headers

Post by sanfordandson » Sat Oct 14, 2017 8:08 pm

va454ss wrote:
Sat Oct 14, 2017 2:14 pm
sanfordandson wrote:
Tue Oct 10, 2017 9:14 pm
We have found good gains with A/R "mufflers" on our circle track engines. Specifically bottom end torque.
Are your gains with a standard collector?
Yes they were installed on a shelf schoenfeld header. 1 5/8 tube 3in collector 9 inch length. I'm sure the gains may be less with a custom header build to a specific application.

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Re: Anti-Reversion Headers

Post by kcengines » Mon Oct 16, 2017 9:18 pm

Can the anti- reversion chambers for primary tubes be purchased or do you have to fabricate your own?

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Re: Anti-Reversion Headers

Post by pcnsd » Tue Oct 17, 2017 12:37 am

kcengines wrote:
Mon Oct 16, 2017 9:18 pm
Can the anti- reversion chambers for primary tubes be purchased or do you have to fabricate your own?
I use these from John Gudenski at Hytech Exhaust (Last name is probably not spelled correctly). I am happy with them. They are $25 each at last purchase plus shipping. They are available in a couple/few material thicknesses. Stainless steel only. Call and talk to him about your project. He was willing to share his experience in application.
http://www.hytechexhaust.com/about_us.html

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Re: Anti-Reversion Headers

Post by NewbVetteGuy » Tue Oct 17, 2017 7:41 pm

I've read the whole thread and it's an incredible wealth of knowledge, diving deep into theory for awhile, but can anyone help bring it back down to practical non-race applications?

When will anti-reversion devices provide the most benefit? My understanding is that the more overlap you have, the more beneficial anti-reversion devices/techniques are.

Has anyone test the benefits on the dyno enough to provide some practical rough guidelines with #of foot-pound estimates for improvement in a few real-life examples?

Where do you see the benefit from said devices? Low-to-mid RPM torque and HP; not at WOT and high RPM (correct?)

What anti-reversion headers/ "mufflers" can actually be purchased off-the-shelf and what items generally have to be custom fabricated?
I've been searching and all I can find for off-the-shelf options so far have been the Shoenfeld and Hendren Racing "mufflers" that attach directly to the header collectors. (The theory is great and all, but I honestly can't find many products to actually be purchased; and exhaust termination boxes even more so, but that's a subject for a different thread...)

The "muffler" versions seem to all increase the diameter on the outlets; does this impact the collector tuned length that should be used at all or is tuning not going to change because of the diameter change?





Getting super practical: Anyone care to wager a guess at how useful the muffler-style anti-reversion devices that attach directly to a header collector would be on a 350 SBC with long runner, single cylinder intake runners (think TPI), with a hydraulic roller cam with 56 degrees of overlap? :D (Can't blame me for asking.)


I very much care about low and mid RPM torque and fuel economy for my build and I've already purchased and installed my headers so the hytech mini-reversion chambers for installing on each header's primary tube is probably "out" for me, although based upon this thread, my guess is that they'd be slightly more beneficial as they're closer to the head...


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Re: Anti-Reversion Headers

Post by modok » Tue Oct 17, 2017 8:21 pm

Interesting questions this month.
Let me let that stew in the brain for a bit and I'll get back to you.
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Re: Anti-Reversion Headers

Post by digger » Tue Oct 17, 2017 8:38 pm

My guess is part throttle will be most beneficial

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Re: Anti-Reversion Headers

Post by tenxal » Tue Oct 17, 2017 9:16 pm

NewbVetteGuy wrote:
Tue Oct 17, 2017 7:41 pm
Has anyone test the benefits on the dyno enough to provide some practical rough guidelines with #of foot-pound estimates for improvement in a few real-life examples? Adam
Tested back-to-back: 1 3/4" dyno headers with standard 4 into 1 collectors, then the same headers with excellent merge collector, then a set of very good 1 5/8"-1 3/4" steps with standard 4 into 1 collector, then the same headers with the previous excellent merge collector and finally Elston Tri Y's with the collector furnished by Elston.

The results show that the theory is fact. :wink:

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Re: Anti-Reversion Headers

Post by MadBill » Tue Oct 17, 2017 9:38 pm

The first test data I saw re A/R headers (circa 1982, AIR) was from a Junior Johnson NASCAR engine. It improved power throughout the whole RPM range but the biggest effect was lowering by about 1500 the minimum RPM at which the engine would accept full throttle; 8-12 HP in the upper ranges AIR, but hundreds at low revs where the standard header combo would not run at WOT.
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Re: Anti-Reversion Headers

Post by joe 90 » Tue Oct 17, 2017 10:35 pm

Here's a few things to think about.

If you've ever pulled a good engine out of a car and fired it up on the ground, you'll know that they don't idle very well.
It's usually due to having no exhaust pipe.
If you refit it (exhaust pipe), then it should idle like a real one.
It's due to reversion.
So....remove the pipe again........back to not idling well.

Go to the next step........remove the exhaust manifold(s).
Fire it up again.........idle is terrible...it won't, got to keep revving it, very little intake vacuum, AFR is all wrong......makes lots of noise, spits flames, annoys neighbours.

A short cam will idle a lot better than a long cam.
Less overlap, less reversion, more vacuum.


Where's the vacuum gone?
The air flows backwards from the exhaust exit, through the cylinder that's got both valves open, into the intake manifold.

An AR header, if done right, it should reduce the backwards flow of air.
If it doesn't do anything, you did it wrong.

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