camshaft advice

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If you do high mileage then the stocker isn't so hard on things. If you are like most Norton owners and only run 1500-2000 miles per year, this likely isn't a factor.
Personally, the thought of a PW3, for example, likely putting extra grindings thru my engine bothers me.

The stock profile was good enough to win quite a few races, so it's not a stodgy old thing. I recall that the 650 ss team(using same cam profile) won the Thruxton thrice and were then asked to go away, please let some other brand have a chance.
It has been said by one very savvy dyno owning Norton engine builder that of all the profiles available, the stock profile gives the greatest grunt in that 4-5 k range.
I would love to test this one day soon.
A friend is building a high compression Combat with a 4s cam. We will test it for midrange on Dyno hill.
I wouldn't expect it to do all that well, but some say the hot cams make more power everywhere. It will be interesting!





Glen
 
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Regardless of your cam/lifter choice it's worth reading up on the correct camshaft run in procedure. Jim Comstock's thoughts on the subject:

"The cam definitely needs run in time of 20 to 30 minutes at engine speeds over 2500 rpm. This is with any new cam -stock or otherwise.
Use a cooling fan or ride the bike to keep the temp under control. Carpet drying fans are cheap.
This process will not hurt the crank or pistons at all -as long as the temperature is kept in check.
Starting a fresh engine with a new cam and allowing it to idle even for a minute is likely to cause early cam death.
I have seen a new cam in car engines mortally damaged by excessive cranking when the guy couldn't figure out why it wouldn't start. [the pushrods were slightly too long] And the thoroughly scuffed cam was still covered with assembly lube."

More reading at this thread:
www.accessnorton.com

Camshaft run in procedure and cam wear

I am anything but an expert, but given the known issue with cam lobes wearing away I wonder what procedure forum members follow when they are running in a new camshaft? My understanding from various sources on the web (including camshaft manufacturers) is that it is critical that the first...
www.accessnorton.com www.accessnorton.com
 
Madnorton said:
AN cams are no longer chill cast iron.
Click to expand...
Indeed. Made out of fresh air it seems (ie not available)! ;)

So, they’re going to be steel nitrided, that’s been common in the Triumph world for a looong time yet the Norton community has long insisted that chilled cast iron is the best cam material.

What’s changed and why the move to steel?
 
worntorn said:
If you do high mileage then the stocker isn't so hard on things. If you are like most Norton owners and only run 1500-2000 miles per year, this likely isn't a factor.
Personally, the thought of a PW3, for example, likely putting extra grindings thru my engine bothers me.

The stock profile was good enough to win quite a few races, so it's not a stodgy old thing. I recall that the 650 ss team(using same cam profile) won the Thruxton thrice and were then asked to go away, please let some other brand have a chance.
It has been said by one very savvy dyno owning Norton engine builder that of all the profiles available, the stock profile gives the greatest grunt in that 4-5 k range.
I would love to test this one day soon.
A friend is building a high compression Combat with a 4s cam. We will test it for midrange on Dyno hill.
I wouldn't expect it to do all that well, but some say the hot cams make more power everywhere. It will be interesting!





Glen
Click to expand...
If you’re gonna test a Combat at least test it as the makers intended surely?

I’m think we’d all agree a stock 850 will eat a Combat in the 4-5k rpm range, as a Combat doesn’t come on the cam until 4,500 or 5,000. If you’re gonna do it (and I hope you do), please also do a test launching it ‘properly’ (if the owner will allow!) and keep it above 5k and let’s see what that performs like.

I am one of those who has said SOME cams can give better mid range AND top end than stock, but I think we’d all agree that doesn’t apply to a 2S, which is an out n out race cam.

I have used a JS #1 in both standard format with 1 1/8” radius lifters and with 7/8“ radius lifters. And as I’ve said before, that cam in both cases produced significantly more forward motion at anything above 3,000rpm compared to a MK3 with peashooters, in a back to back test, with riders swapping bikes. The instant torque from tickover may have been better on the stock bike but it’s honestly difficult to tell because tickover to 3,000 just happens SO fast.

Personally I’m not too interested in grunt from tickover… I’ve got a Harley for that !

But, the cam is only one part of the package. Stick a ‘hot’ cam in an otherwise box stock engine and chances are ‘hot’ will equal ‘slower’ !

Hence we agree, the OP should fit a stock cam, unless he wants to change carbs, port the head, fit bigger valves and raise the compression ratio, etc….

A hot rod Commando is tremendous fun… IF you want a bike like that. A stock easy going torquey Commando is a joy to ride IF you want a bike like that.

Making the ‘right’ choice is therefore all about being as clear as you can with yourself about what kind of bike you want and what kind of riding you want to do.
 
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Fast Eddie said:
If you’re gonna test a Combat at least test it as the makers intended surely?

I’m think we’d all agree a stock 850 will eat a Combat in the 4-5k rpm range, as a Combat doesn’t come on the cam until 4,500 or 5,000. If you’re gonna do it (and I hope you do), please also do a test launching it ‘properly’ (if the owner will allow!) and keep it above 5k and let’s see what that performs like.

I am one of those who has said SOME cams can give better mid range AND top end than stock, but I think we’d all agree that doesn’t apply to a 2S, which is an out n out race cam.

I have used a JS #1 in both standard format with 1 1/8” radius lifters and with 7/8“ radius lifters. And as I’ve said before, that cam in both cases produced significantly more forward motion at anything above 3,000rpm compared to a MK3 with peashooters, in a back to back test, with riders swapping bikes. The instant torque from tickover may have been better on the stock bike but it’s honestly difficult to tell because tickover to 3,000 just happens SO fast.

Personally I’m not too interested in grunt from tickover… I’ve got a Harley for that !

But, the cam is only one part of the package. Stick a ‘hot’ cam in an otherwise box stock engine and chances are ‘hot’ will equal ‘slower’ !

Hence we agree, the OP should fit a stock cam, unless he wants to change carbs, port the head, fit bigger valves and raise the compression ratio, etc….

A hot rod Commando is tremendous fun… IF you want a bike like that. A stock easy going torquey Commando is a joy to ride IF you want a bike like that.

Making the ‘right’ choice is therefore all about being as clear as you can with yourself about what kind of bikeyou want and what kind of riding you want to do.
Click to expand...

I would be happy to test a stock Combat in the same way someday, however this bike is being built from what the owner has on the shelf. I have no control over that.
He happens to have a new 4s cam sitting there so that will go in.
The hill test is just to gather a bit of info on that cam. How bad is the midrange? Maybe it's not that bad and the power above will be fantastic?
Dyno Dave posted the curve for the 4s vs the stock Combat 2s.
The 4 s has twice the number or esses, which makes one think all out race . Actually it is very close in profile to the 2s.
As far as the above 5k launch etc, I won't be asking the owner to let me do that to his newly rebuilt bike.
I'm pleasantly surprised he agreed to the hill test!
I know the hot cams all make a few more hp at top. The OP was asking about a cam for everything but the top range, so that's where my post was aimed.
No one had mentioned the wear and tear factor as most do not think of it at build time.
I once mentioned this on a Triumph site where several posters were planning on removing the stock good for lifetime cam to install a maybe hotter but also maybe less midrange aftermarket cam.
They thought I was crazy to worry about cam wear. Of course it will be fine. Until it isn't.

Glen
 
No doubt cam wear is an issue, on Nortons way more than Triumphs IMHO.

Triumph went with nitrided cams sometime in the early 70s, and they were so good they blocked off the previously added exhaust cam oil feed!

That’s why I asked Madnorton to tell us more about the nitrided Norton cams from AN. Should be a big step forward I think.
 
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I'm very glad to hear that as I used a nitrided cam in the 920. It was sold as NOS, although when it was made is unknown.


Glen
 
I’ve just been listening to the discussion, but went with the stock AN and having mega cycle regrind the lifters as I know it will play well with the rest of my stock components, and similar to fast eddie’s post, if I want a white knuckle ride I can always take out the Ducati.
Thanks again for everyone’s input.
Aiden
 
Aiden said:
I’ve just been listening to the discussion, but went with the stock AN and having mega cycle regrind the lifters as I know it will play well with the rest of my stock components, and similar to fast eddie’s post, if I want a white knuckle ride I can always take out the Ducati.
Thanks again for everyone’s input.
Aiden
Click to expand...
Indeed. Nice thing about relatively stock Norton Commandos is you can ring their necks to the max and still feel relatively in control. I do miss the adrenaline and visceral feel of high HP bikes, but I don't miss the riding position at all.

I can't believe some of these guys my age are still racing around on their clip-on rear set adorned Nortons. More power to them.

Enjoy your build.
 
worntorn said:
If you do high mileage then the stocker isn't so hard on things. If you are like most Norton owners and only run 1500-2000 miles per year, this likely isn't a factor.
Personally, the thought of a PW3, for example, likely putting extra grindings thru my engine bothers me.

The stock profile was good enough to win quite a few races, so it's not a stodgy old thing. I recall that the 650 ss team(using same cam profile) won the Thruxton thrice and were then asked to go away, please let some other brand have a chance.
It has been said by one very savvy dyno owning Norton engine builder that of all the profiles available, the stock profile gives the greatest grunt in that 4-5 k range.
I would love to test this one day soon.
A friend is building a high compression Combat with a 4s cam. We will test it for midrange on Dyno hill.
I wouldn't expect it to do all that well, but some say the hot cams make more power everywhere. It will be interesting!





Glen
Click to expand...
When displacement is increased it effectively reduces the potency of the cam profile. What would be a "hot cam" in a 650 would not have the same torque profile in an 850. I'm finding the torque fall off above 5000 RPM a bit disappointing in my '74 MK II 850. I'm thinking a profile that delivers less cylinder pressure at low RPM might perform very nicely in my 850 with a mild compression increase. More overlap would effectively reduce dynamic compression at lower RPM allowing a bit of "cushion" for lower octane fuels at 10:1 static CR. I had a similar cam profile in 86 Cu In Panhead with 10.5:1 static CR. I could start it with my hand and it would survive on 87 octane fuel as long as I didn't lug the engine. It would come on like a freight train at 3500 RPM and pull strongly to the 5500 RPM shift points.
 
Dan1950 said:
When displacement is increased it effectively reduces the potency of the cam profile. What would be a "hot cam" in a 650 would not have the same torque profile in an 850. I'm finding the torque fall off above 5000 RPM a bit disappointing in my '74 MK II 850. I'm thinking a profile that delivers less cylinder pressure at low RPM might perform very nicely in my 850 with a mild compression increase. More overlap would effectively reduce dynamic compression at lower RPM allowing a bit of "cushion" for lower octane fuels at 10:1 static CR. I had a similar cam profile in 86 Cu In Panhead with 10.5:1 static CR. I could start it with my hand and it would survive on 87 octane fuel as long as I didn't lug the engine. It would come on like a freight train at 3500 RPM and pull strongly to the 5500 RPM shift points.
Click to expand...
I would advise checking out JS Motorsports ‘JS #1’ cam. I thought it was excellent in providing really strong pull in the mid and high ranges but still was a good starter, smooth tickover, etc.

JS also sells ways to raise the CR half a point or so easily and cheaply.

But if you’re feeling flush, his piston and rod kits will also raise the CR whilst making for a smoother motor too.

Well worth checking out if your contemplating a bit of pepping up …
 
Dan1950 said:
When displacement is increased it effectively reduces the potency of the cam profile. What would be a "hot cam" in a 650 would not have the same torque profile in an 850. I'm finding the torque fall off above 5000 RPM a bit disappointing in my '74 MK II 850. I'm thinking a profile that delivers less cylinder pressure at low RPM might perform very nicely in my 850 with a mild compression increase. More overlap would effectively reduce dynamic compression at lower RPM allowing a bit of "cushion" for lower octane fuels at 10:1 static CR. I had a similar cam profile in 86 Cu In Panhead with 10.5:1 static CR. I could start it with my hand and it would survive on 87 octane fuel as long as I didn't lug the engine. It would come on like a freight train at 3500 RPM and pull strongly to the 5500 RPM shift points.
Click to expand...
Dan, that sounds like something else is amiss, not the cam.
The stock cam in an 850 revs and pulls very easily past 6500 as long as there are good twin carbs present and the exhaust is free flowing.

Here's one doing just that.
There's no sense of any fall off after 5000, in fact you need to be careful to avoid going past redline.

To 6500 in 1st and 2nd



Glen
 
worntorn said:
I would be happy to test a stock Combat in the same way someday, however this bike is being built from what the owner has on the shelf. I have no control over that.
He happens to have a new 4s cam sitting there so that will go in.
The hill test is just to gather a bit of info on that cam. How bad is the midrange? Maybe it's not that bad and the power above will be fantastic?
Dyno Dave posted the curve for the 4s vs the stock Combat 2s.
The 4 s has twice the number or esses, which makes one think all out race . Actually it is very close in profile to the 2s.
As far as the above 5k launch etc, I won't be asking the owner to let me do that to his newly rebuilt bike.
I'm pleasantly surprised he agreed to the hill test!
I know the hot cams all make a few more hp at top. The OP was asking about a cam for everything but the top range, so that's where my post was aimed.
No one had mentioned the wear and tear factor as most do not think of it at build time.
I once mentioned this on a Triumph site where several posters were planning on removing the stock good for lifetime cam to install a maybe hotter but also maybe less midrange aftermarket cam.
They thought I was crazy to worry about cam wear. Of course it will be fine. Until it isn't.

Glen
Click to expand...
What I like to do when using the 2S or 4S on the street is grind a 4 inch radius on the lifters. That will give you the advantage of the extra lift without the losses you get with the long duration. That makes for a nice torquey street motor. Then install it with about 5 degrees advance. Jim
 
Dan1950 said:
When displacement is increased it effectively reduces the potency of the cam profile. What would be a "hot cam" in a 650 would not have the same torque profile in an 850. I'm finding the torque fall off above 5000 RPM a bit disappointing in my '74 MK II 850. I'm thinking a profile that delivers less cylinder pressure at low RPM might perform very nicely in my 850 with a mild compression increase. More overlap would effectively reduce dynamic compression at lower RPM allowing a bit of "cushion" for lower octane fuels at 10:1 static CR. I had a similar cam profile in 86 Cu In Panhead with 10.5:1 static CR. I could start it with my hand and it would survive on 87 octane fuel as long as I didn't lug the engine. It would come on like a freight train at 3500 RPM and pull strongly to the 5500 RPM shift points.
Click to expand...
Check the timing, and verify the main jet size.
 
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