Norton intake ports compared to Harley XR 750 (2013)

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http://laurelaluminum.com/

thered have to come a time , when less f'ing around , to knock up a set of patterns , & core patterns , for a virgin to order cylinder head blank .

" If you could start with a 28mm port and create an "m" or eyebrow shape porting upward and wider (not removing material at the guide bore) similar to the harley port mold pics you would be 1/2 way there. Welding up the combustion chamber and adding a fin would allow you to relocate/re-angle guides, install big valves, bathtub chamber, and give you a raised floor to work with & re-radius. You would probably have to weld the sides of the head and re-route the oil return (external line) to get enough oval width. "

anyone there a retired patternmaker / carpenter ?

 
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acotrel said:
You could also add two more valves per cylinder while you are at it.
Wasn't that called the Piper 8 valve Commando head.
Few of those still kicking about, someplace. ?

And doesn't someone (AN ?) have stacks of ONLY right pistons for them, or something similarly 'useful'.
 
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The short life of epoxy in ports has been documented on this forum on many occasions, but has anyone tried these putties or adhesives.
http://www.cotronics.com/vo/cotr/ca_1.htm
In particular the 950 adhesive is meant for aluminium and is good to 1200F. It is an aluminium base adhesive so should have similar expansion to the head.
ando
 

Fullauto

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I was going over this interesting thread again and I thought I'd mention that changing the base casting on Fullauto Technologies heads is not that difficult. Material can be added wherever it's feasible to do so. Also, any of the machining operations can be left out to allow for tuners to do their thing. After all, their are seventeen parts to the core box. Any of these can be changed. So, if you have any ideas on what you would like changed, just put it out there and I'll see what I can do.
 
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You would have to find a way to weld up a stock Norton port or just weld up the combustion chamber and add a fin to get the height you want. Or machine & thread in a whole new large diameter plug for the guide area and use smaller diameter beehive springs (or turn them upside down). Or you could start with the full auto head. It wouldn't be easy. The Harley valves aren't any longer than the Nort valves but I think the make a sacrifice with shorter guides and they wear out in about one race.
I only talked t Herb about the center bearing support.
Someone would have to spec out a Harley ML cam with a harley lifter.[/quote]


Interesting comments on this thread.
DYK when Harley Davison built an 883cc bike for Carl Rayborn in the 1970s they found the inlet ports were so bad that they completely welded them up on a cyl. head and recut them out again to bring them to XR spec.
 
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Hi Jim, what size carbs are they running on the XR 750? I've just been measuring stuff on an A65 BSA head and thought I'd try to get the ports as close to the XR as possible, the bottom port curve I already have close with JB weld in the one I'm measuring which has 44.5mm inlet valves. The top curve won't go quite as high and the width around the guide probably hasn't got the metal. So I cannot get it exactly the same, but it could be more like it than it is now. It's really cool to see the shapes they use and have the actual measurements. I just have 38mm round ports where the manifolds go on, so I'll try changing them to that shape. It will be interesting to see how close I can get it. Do you know if the port shape goes far in the manifold toward the carb?

Thanks for putting the photos and info on here.
 
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I can add 5mm of weld where the spring cup sits and probably get the upper profile. The width around the guide might only go to about 43mm without adding material which could be limited in the pushrod tunnel. It sure is a different sort of shape. Does anyone know flow figures for the XR750 ports? I had a BSA head flow tested the other day but don't have the full data back yet. Plus I'm not sure what he tested it at, I'm hoping 10" otherwise it's not real good.
 

WZ507

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Mark,

The XRs are usually fit with 38 mm Mikuni TMs. With elimination of the restrictor plates they could probably benefit from 40 mm carbs, but likely would not carburet quite as well as with the 38s.

XRs have 44 mm IN valves and a well prepared head flows very close to entitlement for a hemi chamber, in this case ~ 140 cfm @ 10" WC.

XR engines are provided as a pile of parts boxes on a pallet, i.e., everything requires hand assembly. The head comes as a naked machined casting and raw seats, guides and valves are provided but are not installed. Thus, the artist assembling the engine, who does the valve job, has a lot to do with how well the head flows. The late Ken Augustine (creator of the oval port XR head), told me that early on in the oval port days, the MoCo did a valve job on the head and lost ~ 15 cfm airflow. They shipped it back to him so he could modify the valve job and restore the flow, which he did.

You asked about the port shape in the manifold, and in the following picture you can see the transition from faint grey tint to green at the parting between the port and manifold. In the manifold the port transitions from oval to round on the upstream end where the spigot mount carb connects.



Interesting that you're working on a BSA, as that's where the XR head started - with a 350 Goldstar. A winning head wrt airflow (Axtell modified), 8 head bolts for adequate clamping pressure and eccentric rocker shafts for quick and easy valve adjustment (just like Harley ended up with).

Goldstar Head


Goldstar Rocker Box - same long rocker as HD


XR Head
 
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Wow that is so interesting, Possibly the A65s also owe a little to the gold stars in head design. At least with valve angle and dome, my motor is like two B44s. And I use two 38mm TMs. I think the head I had flow tested was done at 10" I had two different port shapes, one was 94.3CFM and the other filled D port was 89.6CFM I haven't got all the data back yet though. On the bike the filled one is better though it's probably not filled quite so much as the one I had tested. A 750 A65 with 80mm bore and 74mm stroke is similar to the XR. We convert the cranks to 90deg and that configuration pulls RPM quite smoothly in the 74mm stroke motor.

I sure feel less awkward about copying a Harley port shape :)

Thanks for the info.
 
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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.



 
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JS
I'm not totally clear what you goal is with the HD cam, to replicate the cam profile, or to replicate the valve lift design, but I think it has to be the latter.

To do this with any degree of accuracy you need to measure the lift at the valve on the HD engine, and from this reverse engineer the data to arrive at a cam profile. Alternatively, by first measuring the cam profile, and running the resulting data through the valve train mechanism, you can arrive at the valve lift design. If you use both methods and the results perfectly overlay each other, you have data you can be confident to proceed with. (Or you have the same errors in both data sets)
The above obviously calls for accurately measuring up the HD valve train mechanism, without it you can only proceed from the lift measured at the valve. Alternately, factory drawings of the layout will be required, but they may be impossible to obtain, so you will have to construct your own.

Having obtained the measured valve lift design data from the HD, to convert this back to a cam profile for use in a Commando engine, again details of the valve train mechanism, this time of the Commando, is needed. Once you have all the necessary data, Prof. Blair's 4StHead software will enable the user to compute all the details for manufacture of the cam profiles.

How it will all work out is something of a guessing game. Good engine simulator software will be helpful to some extent, and 4Sthead would be invaluable in simulating a dynamic run of the whole engine valve train, but it still inevitably ends up as a very expensive exercise to obtain a test camshaft for practical evaluation. You end up at the mercy of the cam grinder who often is not that helpful doing a one off.
 
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Just messing with an old A65 head, seems like I can probably get the port profile top and bottom curves without breaking into the valve spring seat area, though I haven't quite finished. Having the ridge up to the guide keeps the cutter away from the lowest part of the spring recess. The widest area on the plan view I've got to 42mm, so am 7mm too narrow, however it is 10mm wider than before. Ovaling out the port has broken through between the fins on the outer side which JBweld can fix. Need that in the floor as well to bring it up to profile, and to fill parts of the port to get the shape.

Seems like the port chokes down a little where the manifold fits on, a 38mm round hole, which this old head has, looks to have more area. I don't want it too big or I'll have to wait too long for gas speed so if it has less volume there it's probably a good thing.

This data graph shows the difference between an open port head and one with the port floor filled. The filled ports (red trace) flow around 150CFM (converting my figures from 10" to 28"w) The open port around 158CFM but you have to wait. Being a road bike the thing is usually at lower RPM, plus in a corner the more instant response from low revs is a big advantage. So I'm really after the most CFM I can get with out loosing gas speed.


The bike is tall geared, red trace is changing out of second at 99MPH.

 
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Snotzo

It only makes sense to copy the valve action but I’ll be going at it by measuring and comparing the cam profiles and then adjusting according to the rocker arm ratio (the HD has a 1.47 ratio). The HD roller lifter has a .855” diameter roller. I know I have a lot of work to do. I will start with making a lifter and measuring the cam and then adjusting the data to compensate for the rocker arm ratio. This should give me something to compare with the sifter 480 etc. I am working with a new cam grinder who does everything by CNC and he uses 52100 bearing steel. The HD cam was designed by Mert Lawwill and has a very gradual closing ramps to handle the high RPMs the XR750 is capable of. It’s the only cam they found that demonstrated any reliability - but note the failed gears in the photo below. Its developed about as far as it can go for a pushrod motor.



Mark
Are use using my specs or measuring a XR 750 head for the ports? The Norton intake manifold has width limits whereas the HD head has wide manifold ports.
 
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Jim I'm working off your photos and measurements. Which I'm grateful for you posting, really interested to see what it will flow and what it does on the BSA. I'll put some photos up when I get a port done. I'm going to measure it's port volume to compare, which might give a rough guide to the gas speed it will have. The BSA head is possibly less drama than the Norton head to match this port. Just the width near the guide would need some welding in the pushrod tunnel if there's room for pushrods as well. I don't know weather to go so wide because I don't want to loose bottom end. Maybe I should do one wider and one narrower and see the difference in flow.

Peter (who works with the flow bench) has an A65 of 914cc, which flows 188CFM (when converted to 28"w) and puts out 102.8 ft-lb of torque @ 3381. He has made some excellent stuff for his bike. It runs .5" valve lift, has roller rockers and a beautiful 82mm bore alloy cylinder with big fins he made.

With the std rockers I use I don't want to go real high lift, the head I had tested flowed 154.6CFM @ .394" lift and 158CFM @ .436, not much gain for the extra lift. Peter's head flows 180CFM @ .436

Standard A65 inlet port flows 110CFM.

My exhaust ports flow 146.5CFM which may be more than necessary?
 
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mark parker said:
Jim I'm working off your photos and measurements. Which I'm grateful for you posting, really interested to see what it will flow and what it does on the BSA. I'll put some photos up when I get a port done. I'm going to measure it's port volume to compare, which might give a rough guide to the gas speed it will have. The BSA head is possibly less drama than the Norton head to match this port. Just the width near the guide would need some welding in the pushrod tunnel if there's room for pushrods as well. I don't know weather to go so wide because I don't want to loose bottom end. Maybe I should do one wider and one narrower and see the difference in flow.

Peter (who works with the flow bench) has an A65 of 914cc, which flows 188CFM (when converted to 28"w) and puts out 102.8 ft-lb of torque @ 3381. He has made some excellent stuff for his bike. It runs .5" valve lift, has roller rockers and a beautiful 82mm bore alloy cylinder with big fins he made.

With the std rockers I use I don't want to go real high lift, the head I had tested flowed 154.6CFM @ .394" lift and 158CFM @ .436, not much gain for the extra lift. Peter's head flows 180CFM @ .436

Standard A65 inlet port flows 110CFM.

My exhaust ports flow 146.5CFM which may be more than necessary?
I didn't know that the A65 ports were as workable as you say. Tell me if you have my latest CD with 3 different stages of "Narley ports". If you don't then I'll send you an update (send me your email address). Stage 1 and 2 ports are narrower for higher velocity or smaller/mellower motors. Stage 3 is all out screamer close to the XR 750

BTW the A65 I used to own had some flat tracker parts and would blow away Honda 750 fours.
 
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Had some time tonight for working on it. The photo doesn't show the depth very well but the port on the right now has one curve sweeping over the top of the port. The port on the left does not have a smooth sweep, it has compound turns, even when I was filling the floor in other ports it was compound curves, it went up then over the hump of the curve. I now have more JBweld setting in the port floor so I can make one curve sweeping over to the valve, it gets tighter but doesn't reverse direction. This and the need to make it work in this head has the oval port lower as it meets the manifold. It then angles higher and makes one sweeping turn down onto the valve from higher in the head than before. (the lens in my phone doesn't work well for showing the depth)Having the port entry lower I cannot see making a difference but I'm sure the sweep of the port will. Air should make one turn in the port rather than swerving back and forth, and at high speed a smooth turn like the Harley port must be better.

 
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Anyone know what to use to take a cast of a port? Is it just urethane rubber?

Port volume is 5cc less than the 38mm round port. Port is still 6mm narrower either side of the guide, (3mm per side) and slightly smaller at the entry. Still not done but closer.

 
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