What cam do you have and why?

Very interesting variety of opinions and cam grinds. I’m a little surprised that people running some relatively large cams, e.g., 2S, 4S, PW3, 560-00 are so happy with them, since these are not small cams and to some extent will shift the torque peak to higher rpm vs a stock or smaller performance cam. I assume rightly or wrongly that people employing these cams like to spin the engines a bit more than those selecting smaller cams?

Perhaps this falls into the category of beauty and performance being in the eyes (or seat) of the beholder, thus to quote my Canadian friend, “everybody’s got their way eh?” So maybe one person’s nightmare cam is someone else’s dream cam.

comnoz said:

Fast Eddie said:

IF I understand correctly... a WC 312a with radiused lifters has very close lift, duration, and timing to the JS1. So should be a great combo with your FA head IMHO.

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Correction - A Webcam 312a running flat lifters is similar to a JS1. Jim

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Correction accepted sir.

Jim, what effect will a given radius have on the duration numbers?

The stock Commando cam is surprisingly good. When I bought my PR back in '72, I assumed it had the 3S cam, big valve head, and high compression pistons it was supposed to come with. I raced it several times with no mods, and it was quite competitive. When I finally tore the engine down for some mods, I discovered that it had a stock Commando cam and standard head. At least it did have the Powermax pistons it was supposed to. I knew the history of the bike, and the engine had never been apart. It came from the factory without some of the advertised high performance parts. I later learned from a couple ex-Norton employees that it was not uncommon in the shop where the PRs were assembled for them to substitute standard parts if they didn't have the right ones on hand! In any case, my point is that the stock cam is no wimp, and is a decent choice for a street bike. I'm not knocking the use of something like the 2S, Axtell #3, or Webcam 312A with radiused lifters in a street bike. I've tried all three of them in street bikes, and liked the results. I'm just saying that the stock cam is not a bad choice either, particularly if you're on a budget. With a little compression ratio help and 32 mm Amals it will still make good horsepower to 7,000 rpm with no problems.

Ken

acotrel said:

I like Jim Schmidt's go-fast bits, particularly the longer rods and light pistons. However the BSA type cam followers seem to be a pit pointless to me because once you start revving a commando engine over 7000 RPM, you are into a much more expensive game, and do you really need to go there ? The strength of the commando engine lies in it's torque characteristic, NOT top end power. To my mind the 6 speed gearbox is a better investment than the billet crank and thicker cases.

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Nice to see you reminding us of your penchant for E3134 cams and 6 speed gearboxes. At least E3134s are cams, so are related to the topic, especially as I am guilty of not stating Norton in the title.

I am intrigued by the omission of your usual paragraph extoling the steering geometry and general universal superiority of the Seeley chassis though.

Are you simply saving this for later, or are you on the cusp of some new breakthrough?

Fast Eddie said:

Are you simply saving this for later, or are you on the cusp of some knew breakthrough?

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Eddie, your the shits man! :lol: But you forgot the bit about the "point and squirt".

WZ507 said:

Very interesting variety of opinions and cam grinds. I’m a little surprised that people running some relatively large cams, e.g., 2S, 4S, PW3, 560-00 are so happy with them, since these are not small cams and to some extent will shift the torque peak to higher rpm vs a stock or smaller performance cam. I assume rightly or wrongly that people employing these cams like to spin the engines a bit more than those selecting smaller cams?

Perhaps this falls into the category of beauty and performance being in the eyes (or seat) of the beholder, thus to quote my Canadian friend, “everybody’s got their way eh?” So maybe one person’s nightmare cam is someone else’s dream cam.

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The power delivery is very civilized with the PW3 cam, to the point where I wondered why they used such a mild cam in the factory race bikes. One would imagine that something wilder would have been used. However, the proof of the pudding is in the eating, and the motor is very tractable with a good, solid mid range, unlike the Combat (SS) cam where you lost a bit down low (from memory) and then a definite power step at 4500 rpm. In fact, the power with the PW3 is extremely linear.

I'm going for a ride to confirm my thoughts.

Any excuse.

Standard cam for me, as the rest is pretty much standard. Unless you are going to change other items along with the cam - what is the point, a cam alone will give you different - not more as it will not give you something for nothing. to produce more then it will need to be able to feed more and breath more to gain the full benefit. Even a performance cam installed incorrectly will under perform a standard cam installed correctly.

Standard cam in my road bike, with mild porting and .020" over size pistons, makes for a very tractable user friendly all round sport tourer. Fantastic on the hilly twisty conditions of NZ
JS2 (early version) in the race bike, broad spread of power everywhere and makes for a great race motor on short circuits, and also holds it own on the longer back straights. Another user friendly motor and a fun bike to race. As it runs standard sized Vv/s , there is no need for a more aggressive cam.
Regards Mike

Standard cam in my road bike, with mild porting and .020" over size pistons, makes for a very tractable user friendly all round sport tourer. Fantastic on the hilly twisty conditions of NZ
JS2 (early version) in the race bike, broad spread of power everywhere and makes for a great race motor on short circuits, and also holds it own on the longer back straights. Another user friendly motor and a fun bike to race. As it runs standard sized Vv/s , there is no need for a more aggressive cam.
Regards Mike

Looking at rebuilding my 72 Combat I was intrigued by all the options. Based on time and money, I went with a used standard cam and kept the combat head. With 2-1 pipes and carefully tuned stock Amals it is easily the best bike I've owned. The big change was swapping to a 22 sprocket. I just love it. It pulls from idle to about 4500 rpm. It does seem to flatten off a little at the high end, but it has so much torque that over gearing it works perfectly. i don't really see a need to change anything.
The stock combat cam, while maybe a valid design, is made from terrible metal. The one I pulled out was severely worn out, I can't believe I ran it like that... But that's a whole other discussion that's in the archives.

I wonder if anyone on this forum has established a dyno profile for their standard cam, then fitted a race cam and run the motor on the same dyno. And thus established what the change in the dyno bhp and torque figures does for the way their bike performs when it is raced. Or is dyno-tuning mainly about bragging rights ? Perhaps most guys seem to be only interested in improving the top end - that is probably the only reliable figure and even that is usually comparative.
One thing which really strikes me when I watch historic road racing is the number of guys who have got their gearing wrong. On some circuits it is not so critical, but at our local circuit at Broadford - it is very noticeable if you watch the corners. A lot of our racing is 'run what you brung' and changing the gearing can be a bug-bear. My problem has always been about knowing when to raise or lower the over-all gearing - especially with the commando engine where the top of the usable rev-range is limited. With a short-stroke motor the situation is not so difficult.

I don't usually race by following other riders because with a commando-based bike, if you are not on the gas when they are not - you are probably wasting you time. However I WOULD copy this guy :
http://www.bikeexif.com/nyc-norton

Fullauto said:

The power delivery is very civilized with the PW3 cam, to the point where I wondered why they used such a mild cam in the factory race bikes. One would imagine that something wilder would have been used. However, the proof of the pudding is in the eating, and the motor is very tractable with a good, solid mid range, unlike the Combat (SS) cam where you lost a bit down low (from memory) and then a definite power step at 4500 rpm. In fact, the power with the PW3 is extremely linear.

I'm going for a ride to confirm my thoughts.

Any excuse.

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Yep, I loved the power delivery of the PW3 with the Fullauto head and a bit of compression, particularly how it ran from 6 to 7, just such a pity is didn't last long! Jim's spintron may show the reasons for its fragility above 7000rpm. Under that I still think it's a good choice. Enjoy it.

Of course other factors may have impacted the life of the cam, but for my application I am going another direction for durability, but I don't expect much change in performance.

Say SteveA, care to elaborate on:

just such a pity is didn't last long!

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and

other factors may have impacted the life of the cam

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Did your cam lobe(s) wipe out or did you experience valve tangle? I am interested in hearing more on exactly what happened as best as you understand it.

Usually when you fit a hot cam to a road bike, there is a boost in performance both above and below the cam spot. If the cam is too hot, when the motor comes on song, it can come on with a distinct bump which can make smooth riding difficult. These days we have better tyres, however in the extreme racing situation you still end up cranked over on the gas and at the limits of tyre adhesion. Also, these days most racing guys at least use reverse cone megaphones, and especially on four cylinder bikes, exhaust systems in which the header pipes all converge into one tail-pipe. So in effect the bump when the motor comes on song is much more gentle.
The other thing is that a long duration (radical) cam tends to give best power at higher revs. So what the valve gear is doing and how the bottom end of the motor are behaving becomes much more important.
With a commando, the heavy crank and a two into one exhaust tends to stop the power transition when the motor comes on song from being too radical. The worst situation occurs with a short-stroke motor with a light crank, radical cam, open megaphone and sub-standard tyres. A single BHP figure off a dyno doesn't tell you about that.

In Period 4 of Australian historic racing, there are still several methanol fuelled 1000cc Honda CB750 based race bikes which are the main opposition for a commando-based racer. They are nothing like the production racer - CR750. They all have four into one pipes. A CR750 would probably be faster down the straights. There is probably only one A Grade rider who has ridden both configurations. He told me that when he was offered the ride on the current T-Rex Honda, he approached it with trepidation - remembering what the CR750 was like. The current bikes are much easier to ride fast.

In the Australian Superbike Series there is only one privateer who has been relatively successful - he is a dealer in the next town to ours. I was in his workshop a while back when he was working on one of the Honda Fireblades. The top was off the cam-box and I noticed the cams had been welded up and reground. So I asked him what the cams were designed to do. He said 'we change the cams to suit each circuit'. - Easy to do on a Fireblade - not so easy on a Commando ?

My street 850 Commando is stock and quite adequate. If I were to tear it down for a rebuild I would certainly consider a bit more cam in conjunction with getting some squish and increased compression ratio. The Commando head flows quite well.

I campaigned a 750 Commando racer with maybe 9.5 or 10:1 compression, squish and a Megacycle 560-020 cam, and I would have no reservations with doing the same for a snappy street build.

Other race builds were short strokes which utilized Megacycle N480 or D+ Grinds or custom high-speed cams and really have no reasonable application on the street for most people and are certainly beyond the scope of this thread. As a side note, none of them gave anything up on mid range.

Megacycle 560-00 , Dunstall 810, Keihin Cr carbs, my billet steel rods, definitely would use this cam again in a similar setup.

Fullauto wrote;

The power delivery is very civilized with the PW3 cam, to the point where I wondered why they used such a mild cam in the factory race bikes. One would imagine that something wilder would have been used. However, the proof of the pudding is in the eating, and the motor is very tractable with a good, solid mid range, unlike the Combat (SS) cam where you lost a bit down low (from memory) and then a definite power step at 4500 rpm. In fact, the power with the PW3 is extremely linear.

I'm going for a ride to confirm my thoughts.

Any excuse.

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I agree totally with you Ken.
I have said before in previous threads that the 2S does give you the "boost" of power as you get to about 4500 and I used to like this many years ago when I had a 2S fitted, although I was younger then.
I run a PW3 now, and it is very linear in its delivery of power almost to the point of being deceptively boring.
Mine engine doesn't redline in top gear with this cam although I am running a 23t sprocket.

acotrel said:

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THAT is one fine looking motorcycle !!