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Vitesse Mk2 Exhaust Manifold


Mark

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On a 595bhp Ford V8 with 4-2-1 headers, the primaries are 18-20". This for an engine redlining at 8200rpm. First step occurs 8" from the head, then it is 10-12" wrong before merging into the secondaries.

 

One thing of caution about using inlet duct calculators is the speed of sound is different due to the temperature differences.

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That's 4-2-1 on each side?

We're talking about interference extraction here, and that doesn't work on V-8s.

The firing order is variable across engines, but small block Fords fire 1-5-4-2-6-3-7-8.

So with a 4-2-1, the cylinders will be connected 1/2, 3/4, 5/6, 7/8, so they are 180, 270, 180, 45 degrees apart in the fire order.   There's no way that can be accomodated in equal length primaries.

 

Modular Fords fire 1-3-7-2-6-5-4-8, so they would be 180, 270, 45 and 225 degrees apart.

The straight six is unique, not only in having perfect internal balance, but in having an equal phase separation among all cylinders.

1-5-3-6-2-4 allows 1/6, 2/5, 3/4 to all be 240 degrees apart, so that equal length primaries can be effective.

 

John

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See my post above:

 

"You can't use a 1.25" tube and use bend radii large enough to meet the flow requirements of the engine on a 6-3-1 header. 

 

The higher velocity causes a larger pressure drop behind it thus lowering cylinder pressures even further.

The higher velocity gets the exhaust mass further away from the bore before the bad waves come back.

The smaller tube makes for a harder time for the atmosphere to try to get in the 'back door' as it is trying to equalize pressure

Sorry for the triple post - I can't seem to edit them. 

 

Really what you're after is "How small can I keep things without giving anything up at the top of the curve". The large bend radii, packaging, and focus on the port / header transition is what will allow things to remain small without giving up the flow losses to hurt the the top of the curve. 

 

I personally saw an example where there was ~58hp per cylinder feeding into 1 3/8" primaries off the head. It made big gains everywhere.

 

You can and should give up some equal length if it means smoother transitions and not a sharp turn off the head. 

 

6-3-1 is too much not being able to see the forest bust for the trees. 

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Sorry about the empty space above, but the intention was to "glue in" a photo of the exhaust system of the Ford GT 40. Advanced plumbing across to overcome the 90 degree crank of the Ford V8

Later in the seventies Ford had a crate 302 with a flat crank 180 degrees. And just recently the new Shelby has the same. A 90 degree V8 will always need a crossover exhaust to give the last ponies.

Gunnar

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Sorry about the empty space above, but the intention was to "glue in" a photo of the exhaust system of the Ford GT 40. Advanced plumbing across to overcome the 90 degree crank of the Ford V8

Later in the seventies Ford had a crate 302 with a flat crank 180 degrees. And just recently the new Shelby has the same. A 90 degree V8 will always need a crossover exhaust to give the last ponies.

Gunnar

 

These style headers have gone out of style. The primary lengths used to get that pairing only really works for an engine that peaks at 6500rpm and lower. A modern SBF road race engine with iron heads and a low rise dual plane intake will spin to 8000rpm. 

 

Here are some examples of I-6 headers done correctly:

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SteveAmbrose.JPG\\

 

video of the Comp/Eliminator car:

 

they're making over 2hp/ci in that trim. 

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Great, in theory, Gunnar, but then so would be a 5L V-8, with slicks and wings on a Herrald.

 

If you look at the avatar of Gareth Thomas, his avatar is a long primary manifold, designed for but never fitted (AFAIK) to a Vitesse: http://sideways-technologies.co.uk/forums/index.php/topic/6097-gt-claims-and-other-stuff-split-from-the-forum-etiquette-posts/

 

But his magnum opus, actually fitted, was this ultimate curly whirly manifold, with ultra-long primaries:

 

post-690-0-70525000-1459242377_thumb.jpg

 

http://www.jagclub.ru/triumph_tun.html

 

John

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Hello John and Hoffman,

 

Yes simple and effective exhaust is one of the reasons for going flat crank on a V8 ment for racing - from the very start, just as Cosworth, Ferrari Lotus and more. And of course the sound, and the compact light crank, and the lower build. I guess the Le Mans Ford GT 40 gave its best around 6000-7000 rpm. Anyhow the across plumbing gave an aledged  6% power increase over other systems  and a power band with hardly any flatspots. Pulled away from the Ferraris after every corner.

 

Very nice headers indeed. Did you listen to the hakosuka?

 

Gunnar

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Hello John and Hoffman,

 

Yes simple and effective exhaust is one of the reasons for going flat crank on a V8 ment for racing - from the very start, just as Cosworth, Ferrari Lotus and more. And of course the sound, and the compact light crank, and the lower build. I guess the Le Mans Ford GT 40 gave its best around 6000-7000 rpm. Anyhow the across plumbing gave an aledged  6% power increase over other systems  and a power band with hardly any flatspots. Pulled away from the Ferraris after every corner.

 

Very nice headers indeed. Did you listen to the hakosuka?

 

Gunnar

 

The GT40 peaked in the 6400rpm range. They also used FE engines which have a monstrously huge and much too big exhaust port. 

 

A lot has changed with the exhaust port and exhausts and what was done 50+ years ago at this point isn't really relevant. 

 

In that Ford example as above:

 

In-car:

 

Pete%20Halaford%20Motor.jpg

1.65"od x 8" > 1.75" od x 10-12" > 2" secondaries for 12" > 2.25" choke merge > 3" collector > 3" single tailpipe with an A/R chamber just after the Y. 

 

310ci , stock appearing Iron heads, dual plane intake. 595bhp. 

 

Also, in Gareth's test example, it has much larger bend radii than what you can fit when trying to go down and under the car. It makes a HUGE difference. 

 

and yep! It's a good video and Gan San is a legend. 

 

This is a good blog to read:

 

www.exhausting101.com , the site owner is this fellow www.elstonheaders.com . He has NASCAR, NHRA, World of Outlaws, and FIA championships to his credit. 

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  • 3 weeks later...

Hoffman,

 

Triple Y-headers is one way to try to overcome a 90 degree comfort crank. if you want a real racing engine single plane is the only option.. Chrysler did some extensive testing and production of engines with Tri y headers, 1962-64 Max Wedge 413/426. A good friend of mine have a Dodge 1963 with a 413 Scary!

But at present we are far off from the topic of a decent exhaust manifold for a Vitesse.

 

My own wondering is, will a 6-3-1 of a good design always outperform a good 6-2-1 exhaust manifold? Will it give a wider power band, higher top end power or both?

 

Gunnar.

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I have never seen anyone do a compare between the two on the same engine when they haven't changed a 101 other things at the same time making any difference reported virtually meaningless.

 

I was always "told" that the 6-3-1 was very good for mid-range torque, but that a 6-2-1 was better at the top end, so the way I read it if your road driving using torque or your running a 2.5 where adventures into the higher rev band might best be avoided then a 6-3-1 might be the best choice, but if your running a free reving 2.0 where 6K+ is expected to be seen more than once in a blue moon that a 6-2-1 might be a better choice.

 

I run a 6-2-1 which also has some advantages for me as I'm running twin wide band lambada sensors, which means I have a carb, running 3 cyls, matched to the same three exhaust headers so I can adjust and monitor each carb individually rather than just getting some mashed up average of the two which is all you can get out of a 6-3-1 manifold (unless you can install 6 sensors!).

 

I think there are too many variables to say that either would always be the best choice, but if I was building an engine for mid range torque I think I'd try a 6-3-1.

 

PS. On the subject of manifolds, a couple of years ago someone had a bunch of 6-2-1 stainless manifolds for the early MK1 2ltr head ( I think probably ex Falcon ones) that were for sale for ages on ebay, if anyone can remember who it was can they let me know.

 

Alan 

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  • 2 weeks later...

Hi all

 

Here is a couple of pics of my exhaust manifold I have just made and trial fitted to my Vitesse. I made it to fit the 2500s inlet I have but PI throttle bodies also fit. I will have to tweak the next one if I want to use the standard inlet as it just clashes. All primary lengths are equal which took a lot of head scratching. I didn't want to use mandrel bends so bought lengths of pipe and bent them to required shapes by hand. Easier said than done. A lot of trial and error as we all know there are a lot of obstacles in the way and not a lot of space. It appears to  clear everything but not I am not counting my chickens until everything is bolted up tight.  Very happy with the results so far. Ive gone for long secondaries and Just finishing the merge collector. I have already started to make two others, one for my GT6 and another for a future project. I may try a slightly different layout.

 

Mark 

post-741-0-94234500-1462047238_thumb.jpg

post-741-0-10488900-1462047262_thumb.jpg

Edited by Mark
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Yep.

 

After many more failures than success, I think I have finally got the hang of it. 18 metres worth of practice :yes: . Not a total waste some are usable for the other manifolds, some bends which were not quite the right curve may come in handy. I ended up with lots of stubby off cuts, I'll either join them together or make an art instalation.  

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That's awesome! I bet it goes well!

What pipe sizes did you end up using?

 

 

Hi Josh

 

I have been working on the car for the past 10 years, unbelievably, (working on other projects in between)  so still hasn't run. I keep modifying things when I should just get it on the road and then play with things, Thats my intention now. I think the exhaust will help towards an increase in performance.

 

I made an educated guess on what diameter pipes to use after reading and researching lots on various exhaust designs, Jap cars etc. and went for 35mm OD which is 32mm ID primaries with slightly larger secondaries. 

 

I think its about keeping the gas velocity as high as possible without restricting the flow. I think its easy to go to large. I'll have to wait and see until I put it on a rolling road.

 

Mark 

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Oi......! who are you calling a red monkey.... :P

 

Nick

 

Er, nobody west of mmm, mmmm, mmmmm, St. Petersburgh.

 

Hang about, :), an Orange Man is an ape not a monkey!

Edited by pomwah
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