Norton intake ports compared to Harley XR 750 (2013)

lcrken

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Paddy_SP said:
lcrken said:
acotrel said:
FWIW, Axtell's dyno was a Heenan Froude water-brake dyno, not a modern inertial dyno

Ken
Ken - do you happen to know what model of dyno it was? I have a DPX2 in bits which I keep promising myself I'll sort out one day. I used to work on them for a living (at the British Internal Combustion Engine Research Institute), many years ago. After that I moved on to a much bigger H&F 'butterfly brake' which we used for F1 engines.
Sorry Paddy, but I don't know which model it was. I used to have a picture of it showing Axtell at the control console, but can't seem to find it now.

Ken
 
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Thanks for bothering to reply, Ken! Currently, I live in the middle of a village, so the idea of me getting away with running a dyno where I am is a non-starter. We're planning to move before too long to somewhere with no near neighbours though, so if that happens I forecast a dyno cell being constructed! :)
 
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Thanks for taking the trouble to dig the pics out - it's hard to be sure, but that certainly looks like a DPX2! My Lord, I certainly put some hours in on them back in the day!
 
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Bernhard, this thread is really good, it has lots of examples of Norton heads flow tested.

head-flow-testing-t8640-510.html

What I'm experimenting with with the BSA is learning just how the ports effect the engine. What I want to do next is explore making the inlet tract smaller, (not on this big motor, which is good as is, but for a short stroke 750 I'm building) probably by raising the floor higher, with the idea of retaining as much flow as possible but choking down the port so velocity is higher. Other than increase displacement or upping the compression it seems the only way of increasing midrange power. I'm after both effective midrange and top end.
 
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mark parker said:
Bernhard, this thread is really good, it has lots of examples of Norton heads flow tested.

head-flow-testing-t8640-510.html

What I'm experimenting with with the BSA is learning just how the ports effect the engine. What I want to do next is explore making the inlet tract smaller, (not on this big motor, which is good as is, but for a short stroke 750 I'm building) probably by raising the floor higher, with the idea of retaining as much flow as possible but choking down the port so velocity is higher. Other than increase displacement or upping the compression it seems the only way of increasing midrange power. I'm after both effective midrange and top end.
The Narley port CD has 3 versions of ports. All use the same raised floor and smooth radius to the valve seat. But the width and area of the port is smaller in the stage 1 and stage 2 versions to provide higher velocity which moves the powerband lower for those who want more of a boost down there. The stage 3 ports which are shown earlier in this post are for an all out screaming top end HP, high RPM (oversquare) shortstroke.
 
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johntickle said:
How does a guy who can't spell "racing" and doesn't know the dude's name was Al Gunter, not Gunther lay hands on a special piece (if that's what it really is) like this head? And why are Norton and Seeley mentioned in the ad when Gunter raced self-engineered BSAs? The ad says twice that it's used and once that it's new, never used. Sounds like a lot of hooey to me.
 
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I saw an interesting picture today.

It showed the head from a 1965 racing motorcycle and...its inlet manifolds were very, very similar those from an XR750, more extreme if anything. In other words, this design did not originate with the XR 750. This design is at least 50 years old and was EXTREMELY successful then. The picture I saw today was from an engine almost handbuilt in a small Italian town called Vergara.

The head belonged to an MV Agusta MV3 500cc Grand Prix machine.

:D
 

WZ507

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Have a couple comments peripherally related to BSA ports and Jagbruno'ss observation about historical port shapes. But before that want to jump back to an earlier part of the discussion relating to HP.

We can debate ad nausuem exactly what HP a late style XR 750 makes, i.e., who's dyno, who's calibration, rear wheel, crankshaft, etc. That said, I believe it is well accepted that they make somewhere on the order of 100 RWHP give or take. You're definitely not keeping up with an oval port XR on an 85 HP bike. Perhaps the number is 95 HP, or maybe it's 105 HP, but it’s somewhere in that neighborhood. I have not seen unrestricted oval port XRs on a dyno, but I have seen 32 mm restrictor plate engines on a dyno and they made on the order of 85 RWHP. Thus it does not seem a stretch or at all unreasonable to think the unrestricted version could produce somewhere in the neighborhood of 100 HP.

Over the years other marques have made considerably higher power than an XR, but just because a bike makes more power does not imply that that power can be put to the ground efficiently on a flat track or that it can keep up with an XR. Harley stumbled into something quite unique and extremely good for flat track racing with the KR/XR engine configuration (v-twin angle, flywheel mass, flywheel width, power pulse frequency, etc - although recently [last year or 2] AMA made it illegal to twingle them - evidently the race audience hated the sound!). The 100 HP number also comes up frequently, not just for XRs, but for the stroked Kawasaki vertical twins that compete against them and make similar if not more HP. Kawas won all the GNC mile events this year, so they're definitely making some serious power, and as we've noted on the forum in the past, the Kawas epitomize what modern day vertical twin performance can be).

But getting back on track, since considerable content of the present discussion is about port design, and focused on the virtues of the XR oval port head, we tend to overlook the fact that for 15 years preceding the introduction of the oval port, the Al headed XR existed and won myriad races with a round port head, and as has been pointed out previously, it was basically a BSA Goldstar port. Reviewing the past might allow us to see the present more clearly, so to that end am offering a bit of perspective, via the images below, regarding the XR round port that preceded the oval port design of Ken Augustine.

Below are images of castings taken from the late style oval and early style round port heads. In this case, the round port was one done by the king himself, CR Axtell, and from Axtell's numbering system indicates it was done circa 1984 (perhaps lcrken is familiar with the numbering system and can confirm the date code). Flow testing the round and oval port heads fit with radiused entry at 10" WC gives flows of ~ 125 and 140 cfm respectively.

Harley XR round port head ported by CR Axtell


It's interesting to note that the top views of the 2 ports make the late style oval port look gigantic, but in the side view the late style port is shallow and svelte in comparison to the round port. As others have noted previously, the shallow port (top to bottom) allows the floor to be elevated, thereby creating a larger radius curve into the throat area, while simultaneously minimizing the differential in radius between the short and long sides of the port, thereby minimizing velocity differentials between short and long sides as well.

Top view - oval port right


Side view - oval port bottom


Round port - IN left


Oval port - IN left


I have not measured the volume of the oval port along its length, but my intuition is that the x-sectional area of the oval port, even though it looks large and bulbous where compensation is made for the extra volume of the guide and valve stem, is relatively constant along the port's length. The port x-sectional area along its length is something that should be easily assessed by anybody having the SolidWorks database of the oval XR port. Anyone have the database, and if so, could they provide a sense of the x-sectional areas along the length of the port, i.e., from upstream of the guide all the way to the throat?

The images below of the port entry into the head casting show that the elevation of the round and oval ports are essentially identical, thus as described above it is the oval nature of the port that enhances flow by elevating the floor, increasing the short side radius and minimizing the differential between short and long side radii.



 
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jseng1 said:
For those who don't know - I've drawn up the XR750 ports in Autocad and adapted them for Nortons. This info is available on CD (too many drawings to post). A head is being fabricated now. Lots of welding and machine work involved. Presently I'm measuring a XR 750 cam for the same purpose. I could use some help with the cam (I don't have a cam analyzer). I'll try to get as close as I can after compensating for the XR 1.47 rocker arm ratio, BSA lifters etc. We'll see where all this goes.



WZ507 - thanks for the great photos and excellent commentary.
Here's some of the cross sections you're talking about. Its already on page 5 of this thread. The ports shown are XR ports adapted to Nortons. I also have more exact XR specs if someone wants to go that way. Other makes with overhead cams may make more power but no pushrod motor that I know of can make more power than is provided with these ports. I'm hoping someone will build such a "Narley" ported Norton (I'm working out detailed drawings). So far there is one attempt in Australia. Currently I am designing ports that have the potential to out perform even the XR ports (drawings are NOT shown above). It involves adding a fin to the head and lowering the combustion chamber 3/8" of an inch (longer valves). This gives an even smoother radius to the port floor and more velocity. With this latest development it would not be necessary to weld up the port floor because the entire port would be raised in relation to the lowered combustion chamber. This would be for an over-square short stroke with modern parts, heavy duty bottom end and many specs closer to the XR. I've checked with AHRMA and it would be legal.

Its important to understand that the port must go AROUND the guide and the cross section of the port at the guide must be larger to compensate for the area taken up by the guide and valve stem.

Notice the lengthy intake maniolds shown above in WZ507's post. They're about the same length as the Manx intake tract. The only US Norton racer I know about that has this necessary length is the Doug M Commando built by Herb Becker.
 
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This is the BSA with the Harley style port. It still pulls well right through the rev range. The compression ratio is only 9.4-1 at the moment, I didn't realize before measuring it at the weekend, this old head has the valves recessed more than the head I had on before, so I can eliminate one copper gasket and get it back up to 11-1. Which should improve how it all works.

https://www.youtube.com/watch?v=Dz2YhbL ... =autoshare
 
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If I was looking for a good inlet port design for a Commando, I wouldn't look at a Harley XR750. The best ever 350cc single in the 60s was the Aermacchi Ala D Oro which has tapered inlet ports.
 
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My own 850 motor has standard inlet ports except tapered 2mm per side for the first 25mm to suit the 34mm carbs. It pulls like a train, however I use methanol fuel and a skinny two into one pipe.
 
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acotrel said:
If I was looking for a good inlet port design for a Commando, I wouldn't look at a Harley XR750. The best ever 350cc single in the 60s was the Aermacchi Ala D Oro which has tapered inlet ports.
So what power was this 350 Aermacchi single in the 60's making?

The later XR750's were reported at around 100 RWHP. So (350/750) X 100 RWHP= 47 RWHP. Aermacchi's are good but I highly doubt that good. :roll:

I respectfully refer you to the Blowing Smoke thread elsewhere on this forum. :lol:
 
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Something I tried with the Harley style oval port was an experiment to see just what a change to that shape port would do in an A65 BSA head using the same 30mm entry and std inlet valve size. I checked the flow on a std head from 67-69 era and also on a '71 as the porting is a bit different. The '71 flowed 111CFM @ 28"W the earlier head 109CFM bare without carb or bell on the port, both about 60cc port volume. More than stock lift wasn't making a difference.

Between the 30mm round entry and the valve I lifted the port floor and port roof and widened it turning the port smoothly down onto the back of the valve. Port volume still measures 60cc but the flow surprisingly is now 135CFM, if I put a little radius at the port entry 142CFM. I think this is pretty significant and would make the world of difference to a stock A65 and let it make extra power and pull higher RPM without any losses of power down low. It's pretty simple to do and doesn't go near breaking through anywhere, but requires the port floor to be filled and lifted.



84cc port next to the 60cc port. 197CFM and 135CFM I should take a mould of a standard port for comparison.

 
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mark parker said:
Something I tried with the Harley style oval port was an experiment to see just what a change to that shape port would do in an A65 BSA head using the same 30mm entry and std inlet valve size. I checked the flow on a std head from 67-69 era and also on a '71 as the porting is a bit different. The '71 flowed 111CFM @ 28"W the earlier head 109CFM bare without carb or bell on the port, both about 60cc port volume. More than stock lift wasn't making a difference.

Between the 30mm round entry and the valve I lifted the port floor and port roof and widened it turning the port smoothly down onto the back of the valve. Port volume still measures 60cc but the flow surprisingly is now 135CFM, if I put a little radius at the port entry 142CFM. I think this is pretty significant and would make the world of difference to a stock A65 and let it make extra power and pull higher RPM without any losses of power down low. It's pretty simple to do and doesn't go near breaking through anywhere, but requires the port floor to be filled and lifted.



84cc port next to the 60cc port. 197CFM and 135CFM I should take a mould of a standard port for comparison.

Thats a generous radius to the valve and a good eyebrow shape for the roof while preventing the guide area from getting too thin and cracking. And you've achieved significant creased flow with the same port volume.
How did you get in there to fill the port floor? Were you able to weld it? If so - please show us the welding tip.

What is the 197 CFM port about?
 
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The 197CFM port is the bigger BSA port I did before. Like it the floor of this little port is built up with JB weld. Its always worked fine for me but it would be much better if it was welded. Shaping the port is more difficult with two different materials as the JB sands away easier. I have a TIG but even with a stubby electrode I doubt the head of the torch would fit in there. I might investigate it though.
 

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