Norton intake ports compared to Harley XR 750 (2013)

jseng1 said:

Using the XR 750 port specs, intake & exhaust lengths etc on a de stroked Nort could bring new HP levels - possibly enough to blow off the 8 valve weslakes. Centered cam bearing has been engineered to eliminate flex and I think someone has even worked up roller lifters. Maybe use a 270 deg crank. It would take someone with deep pockets and a lot of ambition.

If I find out more I'll post it.

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I am with you on this one Jim. What I see as the big challenges are valve spring pocket to valve seat distance; there is only so much real estate between the two on a Norton head. There are a few tricks that can be played out (including offset and/or raised rocker shafts, different springs, welding up and raising the spring pockets) but those are chump change compared to the real estate the XR head has to work with between the valve seat and spring pocket. Take a close look at the molds you show and you will see it.

As for the middle bearing cam support, are you referring to what I showed you with Herb Becker's handy work or is there another arrangement out there?

Finally, cam loading, cam drive loading and rocker ratios are all challenges to overcome when trying to emulate an XR750. Not saying it should not be tried but there are certainly some challenges there. I know with the ultra short stroke 750 (75mm stroke) we are not far off the mark. With Rob McClendon of D&D cycle as a pilot of the Seeley Norton Rob beat Jay Springsteen on a factory XR 750 at Mid Ohio a few years back.

What would be really handy is if someone has valve lift/crank angle data for one or more of the HD XR750 cams. I have the service manual for all models but it lacks that detail.

So this is fun and interesting but I really need to get back to dreaming.

Dances with Shrapnel said:

Flow testing does not preclude tuning. In other words, no sh*t.

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Indeed. But just doing flow testing and expecting it to make big numbers doesn't always happen ?
Especially if you then stick with the stock inlet and exhaust systems.

Dances with Shrapnel said:

What I see as the big challenges are valve spring pocket to valve seat distance; there is only so much real estate between the two on a Norton head.

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This is why the race guys were hoping that the patterns for the new Norton head castings were going to have an extra 1/2" of metal inserted into the design.

Didn't happen of course, the head had to be compatible with the fitment of what was already out there...

Still we can hope that there might be a few castings with incomplete machining but still the real estate is just not there.

Need a scan of a Commando head, someone with SolidWorks expertise and a 3-D printer for a prototype for casting. Hmmmmmm. With the right team, we could have it by Tuesday.

My thoughts are that it would be best to work within the constraints...sort of. The Norton included angle between valves is a lot less than that of the XR and that tends to exasperate things. The lower included angle does help with respect to when and how much valve acceleration can be tolerated before valve clash. A Norton head flows pretty damn good (which is one of the Norton twins strong points) and before trying to emulate an XR 750 head I would like to have (and may have already) seen a comparison of the flow coefficients for the XR 750 and Commando with big valves. One of the big gains in the shorter stroke engine is being able to use larger diameter valves but a larger valve does not translate to good or comparable flow coefficient without some finessing. And of course there is the translation of flow bench results to actual RWHP gains (or losses).

I think one of the best moves on the part of Full Auto heads is preservation of metal on the port floor. A few on this list know and understand that a lot of air (with good kinetic energy) can flow through a small port with gentle bend. Finessing port walls to accommodate valve guides is one approach and another is smaller valve stems with virtually no guide in the port - but man what a mechanically brutal set up that is.

Maybe emulating some of what was done on the XR750 ports but to a smaller scale (within the constraints of the Commando head real estate) would be a way to go.

Dances with Shrapnel said:

43 races and 3 DNF's - can anyone here say grenade?

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I talked to Mr. Wood about his 1974 racing season and he did not "grenade" any engines, the only problem he had was with the cast Hepolite pistons scuffing and seizing. m With that talent for fabricating drama Mr. Magyar should get a job with Fox News?

It was 42 races, over four times as many races as the "exhaustive" AHRMA roadracing schedule that most of it's racers never complete.

Mr. Wood's Norton was the only Norton to ever win an AMA Grand National dirt track race, and he won the Ascot dirt track championship 3 years in a row, against the best bikes and proffesional riders in the country, not against hobbyists.

The alloy XR750 won the first pro race it entered in 1972, and from there on out made everything else largely obsolete, to the point where Ron Wood ended up trying one.

It got more and more powerful as long as it had to, which ended when the Japanese manufacturers got tired of the AMA changing rules to take a way the advantages they developed in their racers so the Harley could stay competitive. When Honda came out with the RS750 the AMA made everyone run inlet restrictors, which hurt the OHC Honda more than it did the pushrod Harley, also they outlawed 2-stroke multis and who knows what else. The xr750 was making 100 hp by the end of the 70s, and even with the restrictors added later it still made close to that. After 1980 they changed the design of the xr750 engine kit enough that none of it's parts would interchange with those of the original complete bikes that were sold from 1972-1980. The D port xr heads did not appear until after 1980.

I had an original complete 1980 xr750 that I bought 25 or so years ago when they were cheap and rode it around for a year semi-legally on the street and also at the drag strip. I had Carl Patrick in Dayton, Ohio do some work on the connecting rods and big-end bearings of a few other Harley dirt trackers I had with his Sunnen hone. Carl had a modern dyno room he used to test his engine work, he was a go-to man for the Harley Dirt track guys in the East and he gave me a lot of information about xr750 performance and tuning.

The Fullauto head is a great piece of work and we are lucky that someone went to so much trouble for our obsolete engines. I just want the average Norton owner to know that their stock 28.5mm Commando head is nothing to be ashamed of and is a great bang for the buck with fabulous potential.

I think a 28.5 on otherwise Combat could be stupid dangerous move. I've avoided it on my current Combat and leaving the tuned 2-1 exhaust that woke it TF up rusting on my porch.

Commando's came out at the end of the Jet age beginning of the Space age but times changed to current digit netwwwebing age so can pretty much roll your own

http://www.popularmechanics.com/cars/ja ... gy/4320759

This is where I'd start on my next Chopper Cdo....
http://www.wired.co.uk/news/archive/201 ... rinted-car
http://www.explainingthefuture.com/3dprinting.html

beng said:

The Fullauto head is a great piece of work and we are lucky that someone went to so much trouble for our obsolete engines. I just want the average Norton owner to know that their stock 28.5mm Commando head is nothing to be ashamed of and is a great bang for the buck with fabulous potential.

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Ok, who hacked your account and wrote something nice about a Commando? :mrgreen:

beng said:

Dances with Shrapnel said:

43 races and 3 DNF's - can anyone here say grenade?

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With that talent for fabricating drama Mr. Magyar should get a job with Fox News?

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Aha! Faux Entertainment! I knew beng was a fan and one who partakes of the Coolaid.

beng said:

Mr. Wood's Norton was the only Norton to ever win an AMA Grand National dirt track race, and he won the Ascot dirt track championship 3 years in a row, against the best bikes and proffesional riders in the country, not against hobbyists.

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Not to take away from what was done in the past but the power and reliability have been eclipsed...by hobbyists.

beng said:

The alloy XR750 won the first pro race it entered in 1972, and from there on out made everything else largely obsolete, to the point where Ron Wood ended up trying one.

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Have you considered that maybe it had everything to do with the fact that Norton was nearly defunct? Why would Wood flog a dead horse (Norton). There was more potential from that (Norton engine) platform. Just no backing. So again, why would anyone go down a path against a motorcycle manufacture Titan (HD in the states), why? I would say cut your losses and move on. The Norton engine had more than where Wood and Axtell left off; even with welded up (non Steve Maney) cases. We know that already.

beng said:

The Fullauto head is a great piece of work and we are lucky that someone went to so much trouble for our obsolete engines. I just want the average Norton owner to know that their stock 28.5mm Commando head is nothing to be ashamed of and is a great bang for the buck with fabulous potential.

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Unless I have missed something (as I occasionally do) I don't think anybody here was bashing OEM Norton so really no need for you or anyone running to the rescue in their wedding dress. What I see is that the 28.5mm Commando head is not that plentiful for the "average Norton owner". Lots of good performance can be had with a good valve seat cut, little to no port work, bump the compression and then tune the intake and exhaust. Lots of nice torque.

I think the main point in this thread is the opportunities for additional power for those into that sort of thing - not your average Norton owner; although one might find it interesting.

Fair and Balanced - eh?

swooshdave said:

beng said:

The Fullauto head is a great piece of work and we are lucky that someone went to so much trouble for our obsolete engines. I just want the average Norton owner to know that their stock 28.5mm Commando head is nothing to be ashamed of and is a great bang for the buck with fabulous potential.

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Ok, who hacked your account and wrote something nice about a Commando? :mrgreen:

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Only the head. :roll:

beng wrote:

Mr. Wood's Norton was the only Norton to ever win an AMA Grand National dirt track race, and he won the Ascot dirt track championship 3 years in a row, against the best bikes and proffesional riders in the country, not against hobbyists.

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Actually, the David Aldana ridden Norton was the first Norton to win a AMA Grand National event. The Ascot TT July 21, 1973. The Wood Norton victories came later. The riders and mechanics were a pretty close bunch back then and everybody at Ascot that night was glad to see Nick Deligiannis's bike win. Nick's bike had led many AMA Grand Nationals that year only to DNF due to mechanical failure or a crash.

broken link removed

I have some Vincent heads that compare somewhat with the Harley xr 750 heads.
These are Terry Prince heads made to fit onto his oversized 92 mm bore kits (stock bore is 84mm)
They were actually designed by an Australian tuner by name of John Treaste. Some years ago, before designing this big bore head, John designed and built a head for a stadard bore (84mm, same as the twin) 500cc Comet. Standard Comet crankshaft hp is 28, so probably only around 20 rwhp. With Johns head on a standard bore Comet, but with high compression and Prince cams, the Comet produced 58 rwhp!
The interesting thing is the power curve. Instead of producing a large high rpm number at some expense to bottom and midrange power as many race engines do (see Doug Mcrae's 68rwhp graph) ,the Treaste heads produce tractor like bottom end and midrange as well.
Like the Fullauto heads they use a D shaped exhaust port. Inlet ports are 38 mm. Combustion chamber is not hemispherical. Treaste and Prince consider a hemi head to be a relatively low performance head design, even though in auto world it is synonomous with a really high performance engine.
They use a bathtub shaped combustion chamber with a sparkplug at each side. The design also uses quite a large squish band.

It will be interesting to see what kind of output I get from these heads on 1360 cc.
I wonder if anything other than a hemispherical combustion chamber has been tried with the Norton heads.
Are the Harley heads hemis?

Glen







With 10.5 to one CP Carillo piston

beng said:

It was 42 races, over four times as many races as the "exhaustive" AHRMA roadracing schedule that most of it's racers never complete.

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I don't know this for a FACT but am willing to say with some certainty that 42 races included rebuilds, tear downs, inspections, major component replacements (scuffed pistons ) and probably a spare motor. So some fact checking may be in order to see who is wearing the rose colored glasses.

Most AHRMA Norton road racers will go a Season easily without a rebuild let alone a valve lash adjustment. I personally know of a few that went a full season (or as far through the season as necessary to clinch a title) without engine services. Too bad it seems that you have a bone to pick with AHRMA as AHRMA is loaded with fun and sharing people as well as some genuine characters. All are invited to spectate and/or participate as AHRMA is a class act.

rotorwrinch said:

About 15 years ago I paid a visit to Greg Sanders, Long Beach, CA. Greg was the guy who built the one off V4 using two Commando Top Ends. He also was a former employee of Jerry Branch. He showed me a Commando head that had been transformed into a XR750 configuration on one side and still had the Norton geometry on the other. One of the benefits of working in a place like. I have not talked to him in some time. Anyone else been in touch with Greg or possibly seen the Franken Head?

Working on transition to retirement.
Rj Reynolds

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I visited Greg a couple of years ago, and posted some of the info from the visit here

norton-t10174.html?hilit=V4

Greg was as crazy as ever, but busy on other projects, so the V4 was just sitting, waiting for him to get back to some changes he wanted to make. I tried to talk him into selling it to me, but he wasn't interested. Probably just as well.

Ken

Dances with Shrapnel said:

jseng1 said:

Using the XR 750 port specs, intake & exhaust lengths etc on a de stroked Nort could bring new HP levels - possibly enough to blow off the 8 valve weslakes. Centered cam bearing has been engineered to eliminate flex and I think someone has even worked up roller lifters.

Click to expand...

I am with you on this one Jim. What I see as the big challenges are valve spring pocket to valve seat distance; there is only so much real estate between the two on a Norton head.

As for the middle bearing cam support, are you referring to what I showed you with Herb Becker's handy work or is there another arrangement out there?

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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.

There is also the rocker ratio to factor in.

On the 500 ultra short stroke special valve springs sit on steel cups which sit on a land of the guide. The bottom iof the spring pocket could easily be filled with weld or epoxy but I am estimating you would gain maybe 1/8 inch or a bit more in port height but leaving a frighteningly marginal margin to support the guide.

This has me thinking.

JimC said:

Actually, the David Aldana ridden Norton was the first Norton to win a AMA Grand National event.

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Right, Aldana won an actual TT at Ascot, TT races were often won by British bike riders as it was not a horsepower intensive event, but the sort of event that rewards a light machine(non-Harley) with a skilled rider or TT specialist.

Alex Jorgenson was the first to win a flat-track race with a Norton, a half mile dirt track oval, and he did it in 1978 beating a field of mostly XR750s at their own game.

http://www.southbayriders.com/forums/threads/42947/
beautiful bike and is historically significant as the only Norton to ever win a dirt track mile race. It is also the last Norton to earn AMA Championship points. Ridden by Alex Jorgenson and Dave Aldana. Ron Wood's #44 Norton.

Dances with Shrapnel said:

There is also the rocker ratio to factor in.

you would gain maybe 1/8 inch or a bit more in port height but leaving a frighteningly marginal margin to support the guide.
.

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Yes you would have to figure in the rocker arm ratio.

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.

About a centre bearing. A while back I started thinking about building a commando motor with a 6mm chrome-moly plate inserted between the crankcase halves, with a housing fitted to it to hold the bearing. And using separate aluminium barrels supported between a 10mm steel plate top and bottom. Then a staggered XS2 roller crank could be used. I was wondering if a Norton head could be easily converted to cope with the wider spacing of the bores (3mm per side) ?

acotrel said:

About a centre bearing.

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Don't see what this has to do with XR porting in the slightest, but you may recall that Matchless had a bolt-in centre main bearing in their postwar parallel twin twin cranks - and it gave no end of trouble. And wasn't even as smooth as a Norton twin engine. AND, this was in smaller capacity engines than Nortons, well before the Combat saga era....

So, unless you plan to redesign the engine to, say, 961 specs, forget it ?