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I would dare to say the aftermarket for a Norton Commando is better than it ever has been with the number of great restoration and resto-mod parts available.
RH4 To Narley Port Conversion Tubes
- Thread starter maaseyracer
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I would dare to say the aftermarket for a Norton Commando is better than it ever has been with the number of great restoration and resto-mod parts available.
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This image shows the problem with the RH4 head. The venturi should be in the section leading up to the guide - not between the guide and the valve seat. You can see that the 32mm section leading up to the guide is too big. The RH10 doesn't have this problem because it measures 30mm leading up to the guide. Reducing the diameter leading up to the guide increases the velocity, improves the low and mid range yet still provides the top end power of the 32mm RH4 head.
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What works is more important than theory. Extrapolating from what happens on a flow bench might be misleading. When you put everything togther, the package might only suit one application. A 30mm port size might give more versatility, but for a land speed record a bigger port might be better, depending on the gearing, and the run-up to the measuring devices. I do not know the IOM , and what gives the best lap times - quicker through the corners or faster down the straights ?
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Still tracking down a set of 2.5 slides. Found a set of 2.0 slides and filed the cut away from 2mm to 2.5mm. Very big difference. Running a 60 Pilot jet and a yy7 needle, needle position is in the middle, but may need to go a touch richer to yy6. The difference is a very good gain.
While I have been waiting for the throttle valves i drew these up and had these made, these are 3D printed in stainless steel. I have not tested them on the bike yet, as they are not set up for the MK3 exhaust. However, the MK3 version is due back sometime this week from the printer.
While I have been waiting for the throttle valves i drew these up and had these made, these are 3D printed in stainless steel. I have not tested them on the bike yet, as they are not set up for the MK3 exhaust. However, the MK3 version is due back sometime this week from the printer.
Fast Eddie
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Wow they look superb!Still tracking down a set of 2.5 slides. Found a set of 2.0 slides and filed the cut away from 2mm to 2.5mm. Very big difference. Running a 60 Pilot jet and a yy7 needle, needle position is in the middle, but may need to go a touch richer to yy6. The difference is a very good gain.
While I have been waiting for the throttle valves i drew these up and had these made, these are 3D printed in stainless steel. I have not tested them on the bike yet, as they are not set up for the MK3 exhaust. However, the MK3 version is due back sometime this week from the printer.
I made some horrid crude flat washers that look like the end on view of yours. They made zero difference on the dyno! But, of course, they weren’t shaped like yours so could have been causing all sorts of turbulence etc.
Yours look great, I’d love to buy a pair to test out on the dyno…
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If that is the mod which is intended to stop 'reversion', it looks like a good idea. It would cause greater flow towards the top of the port, and increase the pressure of the resonance pulse to return more mixture into the combustion chamber from the exhaust pipe. When the motor is running, on the stroke where both valves are open, there is probably a Kadency effect, similar to that which occurs with two-stroke motors. But an expansion chamber on a four-stroke would be absurd.
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One thing of which I have been very careful - in the outlet from the exhaust port to the exhaust pipes, I have no steps. The ID of the pipes exactly matches the ID of the port at the point where the threads start. I use stubs and slip joints. But I had never thought much about what happens across the top of the combustion chamber when the motor is running. That shaped washer is a very good idea, and inexpensive.
Quantitative assessment might be in your/our future! Eddie, what project might you see the evaluation taking place with?
Fast Eddie
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I’d try them in the 920 which has stock pipes and peashooters, and also in the. 1007 which has a 2:1.
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I am working on figuring out the best way to get the intake tubes to market, there are some challenges with 3D printed parts when it comes to production. The biggest challenge is part consistency and pricing to get consistency.
The exhaust seating is still being worked on and the shape is being finalized for fit on more than one head, the shape being as exacting is less critical on the exhaust side as the seating is only on the floor and not the surrounding port. An interesting issue is the that there is a reasonable amount of variation across Norton heads. 3D printing is not as much in the way on the exhaust seating and 3D printing in stainless steel is probably the best solution here. Ideally I would like to see if there is a reasonable way to get them into production as well.
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Your results are about what I would expect using imagineered anti reversion slugs for your torque torture test. Only thing that would help with acceleration is using a lower gear at the base of that climb. lol
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The raised port floor on both the intake and exhaust is for increasing flow efficiency by giving the floor a more gradual curve. The Harley XR750 has the best cylinder filling and HP output of any 2 valve pushrod twin and part of the reason is the advanced port shape. This is the prefered direction to go as proven with dyno tests. The FA Norton head also has raised port floors for the same reason.
XR750 ex port showing raised floor.
XR750 ex port mold showing side view below - note the gradual curve.
XR750 ex port showing raised floor.
XR750 ex port mold showing side view below - note the gradual curve.
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Yes of course we would all like a shiny new FA head but you can raise the port floors on both the intake an exhaust of a stock head for only a fraction of the cost. See the FA ex floor below - it falls short of the ideal shape of the XR750/Narley port head. The Narley ex port floor is what the slide in insert is shooting for.
The raised ports can be widened at the top around the guide for high performance/race bikes.
The raised ports can be widened at the top around the guide for high performance/race bikes.
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I like that pic with the overlayed ports.Yes of course we would all like a shiny new FA head but you can raise the port floors on both the intake an exhaust of a stock head for only a fraction of the cost. See the FA ex floor below - it falls short of the ideal shape of the XR750/Narley port head. The Narley ex port floor is what the slide in insert is shooting for.
The raised ports can be widened at the top around the guide for high performance/race bikes.
I don't think it's going to be as simple as inserting the plugs or sleeves and some clean up at the edge of the exhaust port plug closer to the valve seat is going to need some attention. Fairly easy to do with epoxy inside the intake port given the flow direction, but not so easy to clean up what would be sort of like a lifted shoe horn edge the flow has to clear inside the exhaust port that has a much higher operating temperature. I'm probably making a mountain out of a mole hill. Carry on.
Here a little something I'm sure nobody gives a darn about: Bob Raber told me the exhaust ports in a Norton head needed to be a little larger to make more power with more cam. He might have been yanking my chain though, and D-ports weren't a well known thing yet then.
If it was as simple as reshaping some metal to get 100 bhp from a 750, you would think Harley would have done that with their various road bike flat tracker lookalike models. Afterall, they have all of the info and moulds.
I suspect that the race engine is setup for lots of power at 7k and up, or perhaps 6 k and up where a flattracker might run. Everything below that might be pretty boggy.
That doesn't mean it isn't worth pursuing this port idea. It might suit the Norton race engines and racers very well.
Glen
I suspect that the race engine is setup for lots of power at 7k and up, or perhaps 6 k and up where a flattracker might run. Everything below that might be pretty boggy.
That doesn't mean it isn't worth pursuing this port idea. It might suit the Norton race engines and racers very well.
Glen
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When I started this post, I pointed this out explicitly, anything I make is
While I know for a fact that the intake ports maximize value, the exhaust port seatings are getting closer...
I like that pic with the overlayed ports.
I don't think it's going to be as simple as inserting the plugs or sleeves and some clean up at the edge of the exhaust port plug closer to the valve seat is going to need some attention. Fairly easy to do with epoxy inside the intake port given the flow direction, but not so easy to clean up what would be sort of like a lifted shoe horn edge the flow has to clear inside the exhaust port that has a much higher operating temperature. I'm probably making a mountain out of a mole hill. Carry on.
Here a little something I'm sure nobody gives a darn about: Bob Raber told me the exhaust ports in a Norton head needed to be a little larger to make more power with more cam. He might have been yanking my chain though, and D-ports weren't a well known thing yet then.
I am not doing anything new, what I am doing has been done for decades on the 351cleveland, they call them, "351 port plates" do a google image search you will see what I mean. I worked for a shop years ago that had a dyno and built historics engines and the owner had a reputation for building 351c engines. we did a lot of experimentation with these especially on street builds or where there was need to keep the engine looking stock, but still make good power. Like all things engine variables matter, and tuning matters even more.
PS These came in the mail today, I should know shortly more about these:
