JS Camshaft profile graphs (2012)

"Too dang tight lifter bores to adapt roller lifters by modifying off the shelf items."

Pic of a Nourish Weslake roller follower along side a standard Norton follower. Weslakes originally used Triumph style (T140) followers but for whatever reason Dave Nourish thought these were worth designing and making. He had to design different cams to match but was able to eliminate the oil feed holes which his original cams have. To me they always looked rather heavy compared to the T140 followers but the valve gear in his engines are good to 10,000+ rpm without float.
Has anyone tried to fit roller followers to the Norton twin?

Seeley Wesslake

Roller lifters as shown above are trick and have advantages but the Radiused lifters are lighter and I get around the oiling problem by drilling the bronze tappet blocks so the oil from the head passes through bronze tappet blocks and dumps directly onto each cam lobe - oiling problem solved - much easier than drilling cams and plumbing for pressurized oil supply. Photo shows oil holes & cam lobes after a year of riding. This lightweight lifter arrangement is a sweet setup and with the beehive springs (which weigh 1/2 as much as stock or RD racing spings) you get a motor that runs more like an overhead cammer. Add the JS lightweight pistons and you are gone.

C.R. Axtell and his partner Mike Libby developed a roller lifter conversion for the Commando, but never marketed it. They used roller lifters that had been designed some time back by one of the SoCal aftermarket cam companies, but I don't recall which. The lifters had been designed for the BSA Gold Star, and Axtell had a box of them left over from the flat track bikes they raced. After Axtell retired (and eventually passed away) Mike continued with the development. He used a bronze insert in the lifter tunnels, much like the BSA radiused lifter conversion, but machined to act as a guide to keep the roller straight. As far as I know, he never ran one in a Norton, but did do a similar conversion for a local Triumph vintage flat track racer, and it worked great. Mike was looking at producing them for both brands, had made the tooling to drill the Norton cylinders for the lifter block retaining screws, and got some bids on making the parts from a local speed equipment job shop, but got stalled by the need to work on paying jobs. I haven't talked to Mike for a couple years, but as far as I know, he never went any further with the project. The lifters looked a bit like the Nourish Westlake ones posted above. The cams were Axtell designs with the lobe shape modified to provide their normal lift profile with the roller lifters.

Ken

Frank Scurria has a Norton 500cc twin racing engine at his house with a roller cam set up in it, but I can not remember if it is Harman Collins or Sparks and Witham. If I get a chance to get any details from him I will....

Ken

Which cam did Mike copy/translate for the roller lifters?

And tell us what you know about the wear rate difference between radiused lifters & flat lifters.

jseng1 said:

Ken

Which cam did Mike copy/translate for the roller lifters?

And tell us what you know about the wear rate difference between radiused lifters & flat lifters.

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I don't recall which grind he used, but most likely the #3. That's what almost all of the customer cams were.

All I know about wear on the radiused lifters vs. flat is from my own experience. I ran #3 Axtell cams with both the radiused lifter profile and the standard flat lifter profile. With the flat lifters I got the usual patch of wear in the center of the lifter. With the radiused lifters I could see where the cam was contacting the lifter by the difference in surface appearance, but there didn't seem to be any wear at all. I had the same result (even contact but no wear) with radiused lifters with the Sifton 460 cams I used.

I'm not sure if there is any advantage to be gained by using roller lifters in a Commando engine, but it looked worth trying. Roller lifters in other engines are popular because they let you use more aggresive profiles, but it takes higher spring pressure to do so. That works in automotive engines where the cam is well supported, the pushrods are sturdy, and the lobes and rollers can be relatively large in diameter. In the Norton, with its small lobes and long, unsupported length, I'm not sure you can gain much. Adding a center bearing support for the cam, as a couple people here have already tried, should help, the combination of long rockers, flexy pushrods, and small lobes seems to me to be the limiting factor in how much spring pressure and lift acceleration you can use. Right now, the radiused lifter seems like a good solution for Norton race engines. The only improvement over the BSA lifter conversions would be a larger area on the base of the lifter, sort of like the Triumph practice back in the day of fitting Thruxton tappets to the 500 and 650 twins. As I recall from posts here (dances with wolves, I think), Herb Becker developed something similar for Nortons.

I'm pretty sure if someone developed a roller cam setup for Nortons at a reasonable price, it would sell well just for the bling factor.

Ken

jseng1 said:

Photo shows oil holes & cam lobes after a year of riding.

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Lets see, there are 8760 hours in a year, times 40 miles per hour average means you put 350,400 miles on the cam. Wow, it does look good for that much use.......

Which yes, is my way of saying that "a year of riding" does not really tell anyone anything.

Attention: Ken and all of the Southern Caifornia guys, On May 12, They are going to have a Flat track reunion for all of the Ascot riders, Tuners and Fans. It will take place at the Wally Parks N.H.R.A. Motorsports Museum 1101 West McKinley Ave. Pomona, Ca. 91768-1639 (909) 622-2133 May 12, 2012 (9am-4pm) Admission is $10.00 and benefits, Aid To Injured Riders. And if you would like more on Sunday May 13, The SCFTA will hald a special Ascot Tribute Short Track race at Perris, Ca- perrisflattrack.com. May be a nice place to talk to some of the old riders builders and tuners. Have a great day and ride safe, Chuck.

Which yes, is my way of saying that "a year of riding" does not really tell anyone anything.

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Well one must realize rider JS rev's the living snot out of his test bed bike, so even one of his outtings may equal a seasons lifter war on yours or mine. I'll shortly have a look in at new surfaced flat lifters of prefectly normal range of Combat usage, never red lined but maybe last time out smoking, never held on till topped out, 110 mph tops a few tunes, saving tires and chain and gear box, over ~7000 miles - to see how obvious which lifter type wears better. Then will repeat Comstocks experiment with cam oil feed to flat lifter Peel. If don't work out, heck only $700 or so to try JS's BSA set and new cam.

beng said:

Lets see, there are 8760 hours in a year, times 40 miles per hour average means you put 350,400 miles on the cam. Wow, it does look good for that much use.......

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The test bike is a street racer. There is no odometer so I don't have a mileage figure. It gets ridden about 2 or maybe 3 hours a week and occasionally to its limits. Guess what an average year of riding would be, look at the cams lobes in the photo a few posts above and you will get my point about reduced wear with cam lobes designed for radiused lifters.

beng says - "8760 hours in a year" (equals riding 24 hours a day).

I’ll get right on that when I can find the time.

Ah shit Jim, never saw your long suffering desert street fighter in this ratty minimalist light before : )
=Also acknowledging the D vs D+ non-issue and ura flat tap/cam comb delivering the valve action Peel seeks, ie: not maxed out on anything to risk much with. Once I ever get a feel for Peel flow envelope its likely may want to change cam profile so keeping your price of that ticket in mind for priorities. Also in back of mind even before BSA-radii's is asymmetric cam profile, just don't know what's involved to do so or how skewed to go. Glad I jumped on your garantee'd D+flat cam while available.

Steve,

what got you so excited about asymmetric cam profiles? Do you know of anyone doing them for Nortons? Axtell used to grind what he called his Allegro cam with asymmetrical lobes, but I don't know if those ever went into anything besides Ron Wood's bikes. I'm a little fuzzy on the details (it's been 35 years or so since he told me about them) but it had to do with being able to let the valve close more rapidly than it opened, because you have spring pressure helping close it. You can do some interesting things that way with radiused or roller lifters, but it requires useing a smaller than normal grinding wheel on the cam grinder, and most cam grinders weren't willing to do that back in the day. That's one of the reasons Axe finally got his own cam grinder. Wish I had more detail, but that was a long time ago.

Ken

Uhh, what I had more in mind than skewed lobes was completely different intake vs exhaust shapes for my pecial application in boosted Peel whose main heat pressure flow hang up is getting the exhaust out as fast as forced in. Too bad JBW ain't up to this.

Just terminology, then. Asymmetrical as applied to camshafts means a lobe profile that is not the same on opening and closing sides. Different intake profiles and exhaust profiles on same cam is common, and not asymmetrical. Most of Norton's factory race cams are like that. Most cam grinders are willing to let you select different profiles for intake and exhaust to fit a special application, as long as you seem to know what you are doing. I recall Norris doing that with Norton cams, using an intake profile from one of their off-the-shelf cams and an exhaust profile from a different one. I think Jim Schmidt might have had some experience doing that with that Norris, back in the day, but, once again, my memory is a little fuzzy on the details.

Ken

Ok had to catch up my cam terminology. When both exht. and intake lobes are the same shape but lift side is different than let down side its called and asymmetric profile. When the intake lobe shape differs from the exhaust lobe its called a dual profile cam.

Tip 6: In the area of single- and dual-pattern camshafts, controversy seems to reign supreme. Proponents of the dual-pattern grind feel that a standard pushrod engine will breathe better on the intake side than it does on the exhaust side. In this scenario, the exhaust lift and duration figures are greater in order to compensate for the exhaust port’s inability to breathe. The single-pattern group points out that the exhaust is somewhat controlled by cylinder pressure. The piston movement helps to force the exhaust from the combustion chamber and, as a result, the intake port does not have any real advantage. This makes for a single-pattern camshaft that features identical intake and exhaust lobe profiles. Which is the better of the two designs? Both have merit. Your particular combination might respond properly with a dual-pattern cam grind while a slightly different Chevrolet might show promising results with a single-pattern grind.
Read more: http://www.hotrod.com/techarticles/cams ... z1qqrE6aj0

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Cam Accordingly
Just as you don't want a high static compression with a supercharger, you don't want a long-duration, big-overlap camshaft, either. Since the incoming air is under pressure, the intake valve opens as the mixture rushes into the cylinder. If the exhaust valve is open, a portion of the air/fuel mixture will be pumped out of the exhaust system by the supercharger. In general terms, a camshaft with less than 240 degrees duration (measured at 0.050 inch lift) will work well. Camshaft overlap should be minimized with lobe centers in the area of 112-115 degrees. Many street-blower cams are ground on a dual-pattern profile to allow the exhaust more duration than the intake (with the intake closed). This is because the blower pumps more air/ fuel mixture into the cylinder on the intake stroke, but the exhaust needs to exit on its own, so the exhaust duration is increased. Most camshaft manufacturers offer cams specifically designed for blower motors.

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lcrken said:

Different intake profiles and exhaust profiles on same cam is common... I think Jim Schmidt might have had some experience doing that with that Norris, back in the day, but, once again, my memory is a little fuzzy on the details.

Ken

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I used to grind a smaller radius on the exhaust lifter so it would have less duration than the intake. It would have the same lift but with the reduced duration there was more valve clash clearance. Clash clearance was always a problem when using bigger valves and wild cams and this usually solved the problem. I would leave the intake alone to get all the duration I could on that side. The accelleration rate would increase on the exhaust but that valve is smaller & lighter so you could afford a more aggressive ramp without getting valve float.

With my 850 monoshock (photo below) - on checking after a race I once found that my valves (which had.050" valve clash clearance) were floating & rubbing each other and the pistons (.050") squish clearance were hitting the head. I raced without a tack and the RD racing springs with the original heavy flat lifters couldn't keep up with what I was doing to the motor. Experiences like this are what pushed me toward the lightweight radiused lifters, beehive springs and lightweight pistons etc.

Ken -

Over scotch one evening, Ax also tried, through one of his table top chalk talks, to convey to me what he was trying to do with his cams.

All I remember was that his object (in addition to making power) was controlling the path of the valve train. He was shaping the cam's profile, both on opening and closing, to minimize loss of control, such that if/when the opening valve train was oversped and tossed/disconnected from the cam, the cam/lifters' shape, by the way they tossed and then caught the rest of the valve train, would allow the valve train to land smoothly on the closing ramp; he wanted it all to be able, if need be, to fly but then to settle back onto the closing side without shock or bounce. He was shaping the cam by what he could read from the witness marks on the lifters, cams, and valve seats.

Thanks, xb. That sounds pretty much like what I remember. I also remember him telling me that he found some info in an Italian book on camshaft design that he thought everyone else had missed, and that he used in the design of his cams. It might have been that flat top he left on his cam lobes. I remember him telling me that it "let the valve springs rest." I never did get the name of the book. He was quite the guy. I also recall sitting around with him and Mike and sipping booze out of coffee cups after work, and talking to him about everything from .22 pistol shooting to bicycle riding. Mike also had some pretty good stories from his racing days, if you could get him talking, but the subjects were a lot less respectable.

Ken

xbacksideslider said:

Ken -

Over scotch one evening, Ax also tried, through one of his table top chalk talks, to convey to me what he was trying to do with his cams.

All I remember was that his object (in addition to making power) was controlling the path of the valve train. He was shaping the cam's profile, both on opening and closing, to minimize loss of control, such that if/when the opening valve train was oversped and tossed/disconnected from the cam, the cam/lifters' shape, by the way they tossed and then caught the rest of the valve train, would allow the valve train to land smoothly on the closing ramp; he wanted it all to be able, if need be, to fly but then to settle back onto the closing side without shock or bounce. He was shaping the cam by what he could read from the witness marks on the lifters, cams, and valve seats.

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Quite likely not related at all, I never bothered to get my head around it, but I have a bike that has concave flanks on the cam lobes

Why are Norton camshafts all at the same lobe centre? Is it 106 degrees?

If you were using a camshaft specifically designed for a short stroke engine, wouldn't the lobe centre change because of the higher revs?