Cams (2012)

worntorn · Apr 6, 2012

With the stock bikes, other than the combat models, were there any cam changes thru the years or is it all the same basic profile from the first 750 commandos thru to the last 850 models?

Glen

comnoz · Apr 6, 2012

worntorn said:
With the stock bikes, other than the combat models, were there any cam changes thru the years or is it all the same basic profile from the first 750 commandos thru to the last 850 models?

Glen

For all practical purposes they were the same.
I have seen some MK3-850 cams with slightly more duration @ .200 but I don't know if it was a design change or just a variation in manufactures. Jim

ando · Apr 6, 2012

Jim
Would you have a graph of a 4s vs a Webcam12a. You have obviously run both in your road bike. Can you please tell me the difference between them, road performance wise, (particularly relating to 810cc at 10 to 1). thankyou
ando

comnoz · Apr 6, 2012

ando said:
Jim
Would you have a graph of a 4s vs a Webcam12a. You have obviously run both in your road bike. Can you please tell me the difference between them, road performance wise, (particularly relating to 810cc at 10 to 1). thankyou
ando

I don't have a graph of a 4S. I had one I had done manually many years ago but it has been lost. Dave has a graph here:
http://atlanticgreen.com/images/cam440.gif

The 4s is more race oriented than the 12a. The powerband is narrower.

The 12a has a bit more overlap and closer lobe centers. You often need to sink the exhaust valve to get enough valve to valve clearance. The 12a is more touchy as far as exhaust tuning goes.

I like the 12a better on the street and had very good luck with it in the racebike on short tracks. It is easier n the valvetrain than a 4s. Jim

comnoz · Apr 16, 2012

Here are a few more cams.
First is Debby's unknown cam. It looks like a Megacycle 560NR grind although the duration at .040 is about 5 degrees short of the advertised duration. Lobe centers and lift match at .350 lift and 104 centers.

Here it compared to a Webcam 12- the 560nr is a bit hotter

Here is the 560NR compared to a webcam 12A- the 560NR is a little softer

And here are the 4 JS grinds graphed together. The JS0A, the JS1A, the JS2 and the JS3

Bernhard · Apr 17, 2012

Interesting topic on the subject of cams, just to throw a spanner in the works what is the best cam to use in a 500 Domi with a 650ss head :?:
I know that this belongs to the Classic page but there are far more people disusing this topic on the Commando page.

beng · Apr 17, 2012

Bernhard said:
Interesting topic on the subject of cams, just to throw a spanner in the works what is the best cam to use in a 500 Domi with a 650ss head :?:
I know that this belongs to the Classic page but there are far more people disusing this topic on the Commando page.

You could not go wrong using the stock Dominator camshaft in a 500 dominator. It worked well on the street and well on the track. That is a small motor, so the Dominator cam will look a lot bigger to it than it will to a 650 or 750.

You have probably seen me post info before about the 1964 Daytona racers that Dunstall screwed together for Berliner Corporation to race that year. Using the stock cam with small Amal Gps, a skimmed cylinder to raise compression, a flowed head and open exhaust they got about 54 hp at the crank at a realistic rpm. A nice figure for a "racing" engine built from all production parts!

I just think it is really interesting the power that can be pulled out of a Norton engine by just massaging what it came with from the factory, like "comnoz" talks about how good the stock cam is even for an 850, and how he would mill the head.
He could probably put a 750 or 850 Norton engine together with all stock parts that would have more power than a lot of "race" engines guys have put together in the past stuffed with trick aftermarket parts. Am I right?

Using all stock parts has the added benefit of low initial cost.

As always there is more to be had at higher rpms with a bigger cam, but then you are talking about using expensive custom parts, and probably using them up quickly.

comnoz · Apr 17, 2012

Bernhard said:
Interesting topic on the subject of cams, just to throw a spanner in the works what is the best cam to use in a 500 Domi with a 650ss head :?:
I know that this belongs to the Classic page but there are far more people disusing this topic on the Commando page.

For race only looking for power from 6000 and up I would probably be looking at a Webcam 30. It has lots of duration but limited lift. Jim

johnm · Apr 17, 2012

Bernhard said:
Interesting topic on the subject of cams, just to throw a spanner in the works what is the best cam to use in a 500 Domi with a 650ss head :?:
I know that this belongs to the Classic page but there are far more people disusing this topic on the Commando page.

Unfortunatlely the answer is a question. Best for what?

Based on 10 years racing 500 Domi with an SS head I suggest the following:

For the street and an average rider on the track a mild cam.

For a machine ridden by a very good rider preferably with more than 4 speed box, 10.2 :1 compression, dyno developed megaphone exhaust, reworked head and D'd exhausts etc use a PW3 cam installed straight up or with a little retard. This can have 50 bhp at the rear wheel at 6000 rpm. Below 4000 rpm it will have nothing.

John

beng · Apr 17, 2012

Anyone ever use a Johnson cam for a Norton as here?:

http://www.johnsoncams.com/jc_n_cams.html

They have a nice selection and also look to have the best prices in the business.

comnoz · Apr 17, 2012

Here is the Webcam 18a grind with BSA lifters compared to the Webcam 12A with flat lifters. Basically the same. The 18a with BSA lifters is what has been in my bike for several years. It is very top end oriented. Jim

worntorn · Apr 17, 2012

comnoz said:
Whitworth Ranch said:

Curious what cam is likely to be in my '74 850 Roadster. I know the head is an RH10, but I don't know if this has any bearing on the cam. Does someone know what is probably inside? Pretty sure the engine has never been apart.
Mark

Click to expand...

It would have came originally with the stock Commando cam. The same as the 71 Commando cam shown.

Actually the stock cam is a pretty good performer. The first thing I would do to add a bit more performance to that bike would be mill about .040 from the head. Jim

I see there is an .003 copper headgasket available. Any thoughts on using this to raise comp on an 850 instead of milling?
With the full thickness copper gaskets at around. 040 changing to this gasket ought to bring the comp up quite a lot, Im guessing to around 9.4 from 8.5.

Glen

jseng1 · Apr 17, 2012

For comparisons:

The webcam 18A is about the same as the JS1 cam a (both use lightweight BSA lifters). The Axtel #3 has about the same profile with flat tappets and is about the same as the Webcam 12A with flat lifters.

And yes the JS .003' thick headjasket ring avoids having to mill the head. I use one on the street and the Dan Rose bike that won Daytona with Maria Costello this year used it.

pommie john · Apr 19, 2012

worntorn said:
I see there is an .003 copper headgasket available. Any thoughts on using this to raise comp on an 850 instead of milling?
With the full thickness copper gaskets at around. 040 changing to this gasket ought to bring the comp up quite a lot, Im guessing to around 9.4 from 8.5.

Glen

Where can you get these?

jseng1 · Apr 19, 2012

I see there is an .003 copper headgasket available.
Where can you get these?

JS .003" copper rings are available at:

http://www.jsmotorsport.com/products.asp

more info about them at:

http://www.jsmotorsport.com/technical_compression.asp

B+Bogus · Apr 19, 2012

comnoz said:
I have never seen a 3s. Jim

I pulled this 3S out of a pretty derelict bottom end - I'm inclined to get it re-stellited and see how it performs.
It's parked next to a 'popular' cam from the White Rose County.
Legend has it that the Yorkshire rose is white because it was the cheapest :mrgreen:

The lift is 0.366" inlet and 0.321" exhaust. The new cam is only 4 thou bigger on the inlet and 2 thou on the exhaust.

Regards, From the Red Rose County.

Dolis · Jun 28, 2012

Hi,
very good thread, learned a lot.

I have questions about my comming street combination:
880 cc, ported head, 2S cam, CR 10:1, 36 mm flatslides.
Exhaust: 38 mm with reversed cone.

I´m a bit worried it should be a bit peaky.
Do you think I had to worrie about that with 880 cc?

I´m thinking of advancing the cam a little, say 3°, to gain a bit of torque in the bottom.
Has any one tried that?
Any opinion?

Chris

comnoz · Jun 28, 2012

Dolis said:
Hi,
very good thread, learned a lot.

I have questions about my comming street combination:
880 cc, ported head, 2S cam, CR 10:1, 36 mm flatslides.
Exhaust: 38 mm with reversed cone.

I´m a bit worried it should be a bit peaky.
Do you think I had to worrie about that with 880 cc?

I´m thinking of advancing the cam a little, say 3°, to gain a bit of torque in the bottom.
Has any one tried that?
Any opinion?

Chris

The 2S cam will be a little peaky. It will trade a bit of below 4500 rpm power for more power above 5000. Not a bad street cam if you ride in a sporting manner. The fact that the engine is larger does not mean the cam "comes on" earlier but the

fact that the engine is larger does make up for some of the lower RPM loss. It would likely be better on the street with some advance- maybe even up to about 10 degrees.

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

marinatlas · Jun 28, 2012

Hi, is someone able to tell me the radius of the BSA cam followers??

Dolis · Jun 28, 2012

The 2S cam will be a little peaky. It will trade a bit of below 4500 rpm power for more power above 5000. Not a bad street cam if you ride in a sporting manner. The fact that the engine is larger does not mean the cam "comes on" earlier but the

fact that the engine is larger does make up for some of the lower RPM loss. It would likely be better on the street with some advance- maybe even up to about 10 degrees.

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[/quote]

Thanks Jim!
I might try that.
Is there really a big differens on the road between the 2S and 4S?
I´m very satisfied with my 4S in my 828 cc engine.
When I first tuned it, from std 750, I felt I gained a lot of power all over.
I believe the exhaust is the same but the intake differs with less duration on the 4S.
Chris

Cams (2012)

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