Cams (2012)

comnoz · Apr 3, 2012

Here is some of the more popular cam graphs I have compiled.

First is the PW3 vs Js2 , they are nearly the same. The pw3 has a little more lift and the js2 has a little more overlap. I would expect similar performance.

Next is the Norris D+ vs the Megacycle 560N480

Here is the Megacycle 560N480 vs the Webcam 197 with a 4 inch rad lifter, Nearly identical but the 197 uses less valve lash.

Here is a standard 71 Commando cam vs a Webcam 12A [my favorite hot street grind}

Here is the standard 71 Commando cam vs the Webcam 12 [excellent replacement cam that gives a mild performance boost on an otherwise standard engine]

Here is the Norris D+ compared to the standard 71 Comando cam.

Here is the standard 71 Commando can vs the 72 Combat 2S cam

Here is the PW3 vs a Webcam 86C+5 [my favorite fast roadrace cam- for big tracks]

Here is the WC12a vs PW3.

I have a few more varieties that would need to be converted to JPG if you have any requests. Jim

debby · Apr 3, 2012

Jim,

Could you do one comparing Webcam 12 to Megacycle 560NR?

thanks,
Debby

comnoz · Apr 3, 2012

debby said:
Jim,

Could you do one comparing Webcam 12 to Megacycle 560NR?

thanks,
Debby

Debbiy,
I don't have a graph on a megacycle 560nr but I recall it is nearly the same as the webcam 12.

If you have one loose I will gladly graph it. Jim

Hobot · Apr 4, 2012

The best results I have had for a blower cam has been short duration with wider lobe centers for less overlap.
If you are using high compression along with limited boost from a positive displacement blower you might want a little more cam. Jim

Hmm, + displacements are heating compressors not cooler snail fan blowers like Drouin.
I figure to hit the speeds I want Peel to do requires like 1hp per 4 lb of bike/pilot and to accelerate to that speed requires like 1 lbft torque per 4 lb total mass. So shooting for 140 hp/120 tq. with 500 lb combo by 7000 rpm. The model I'm trying to follow is a 'hi' CR n/a hot cam big block that adds low rpm boost that comes on 'slowly' but rises fast. The standard wisdom to cam a mechanical drive compressor is nil over lap so it don't blow most the boost right out the window. The standard wisdom for a rpm-heat flow driven turbo blower is nil over lap cam so the back pressure don't over come the boost fed in. CR must be lowered in these cases or they spike compression too soon and detonate. Mercedes Kompressor cars are Hi CR low boost pump gas example. I can't hardly think/find an example more complex than Peel's engine to solve or ruin. Here's a study to consider and slap me back on my misconceptions please. Big block w small chamber and valves.

The exception to the rule:
Sometimes people take a car that starts off with a 9000 rpm redline, has an 11.5:1 compression ratio, and a 280* duration camshaft, and an aggressive naturally aspirated-esque timing curve and decide to supercharge it for more power. One such example is kleemann's kompressor for the SLK55 AMG (which already makes 400 hp in normally aspirated form from an 11:1 compression ratio motor). In this type of application, if you use a more conservative cam, and dial out all the overlap, and increase the power stroke, in combination with an already high 11:1 compression ratio and a healthy amount of boost pressure (7psi or above) you will end up with a motor that produces extremely high peak cylinder pressures and those intense pressures and heat may easily start off a chain reaction of pre-ignition and detonation and you will find that no matter how much you retard the timing that the setup will end up both powerless and still not that safe.

In this case, I would consider RPM and compression my primary power adder, and my supercharger as my secondary power adder (that is unless I decided to change that and went ahead and lowered the compression ratio of the motor). In this case it is ok to sacrifice some supercharger high rpm efficiency for preventing high-load & low-rpm detonation. Furthermore, to overcome the overlap inherent in this kind of high rpm normally aspirated power-plant it would be very advisable to use a centrifugal supercharger that is capable of producing more boost and flow with increased rpm rather than a roots type charger that will easily run out of boost and flow capacity (CFM) when facing an aggressive camshaft 'leaking' boost away.

Article Source: http://EzineArticles.com/2473412

Meercedes Kompressor cam profile to ponder
http://www.planetsupercar.com/forum/sho ... 791&page=1
http://www.execstudio.com/products_pack ... _power.htm
http://mbworld.org/forums/c32-amg-c55-a ... -cams.html

Hobot · Apr 4, 2012

The best results I have had for a blower cam has been short duration with wider lobe centers for less overlap.
If you are using high compression along with limited boost from a positive displacement blower you might want a little more cam. Jim

Hmm, + displacements are heating compressors not cooler snail fan blowers like Drouin.
I figure to hit the speeds I want Peel to do requires like 1hp per 4 lb of bike/pilot and to accelerate to that speed requires like 1 lbft torque per 4 lb total mass. So shooting for 140 hp/120 tq. with 500 lb combo by 7000 rpm. The model I'm trying to follow is a 'hi' CR n/a hot cam big block that adds low rpm boost that comes on 'slowly' but rises fast. The standard wisdom to cam a mechanical drive compressor is nil over lap so it don't blow most the boost right out the window. The standard wisdom for a rpm-heat flow driven turbo blower is nil over lap cam so the back pressure don't over come the boost fed in. CR must be lowered in these cases or they spike compression too soon and detonate. Mercedes Kompressor cars are Hi CR low boost pump gas example. I can't hardly think/find an example more complex than Peel's engine to solve or ruin. Here's a study to consider and slap me back on my misconceptions please. Big block w small chamber and valves.

The exception to the rule:
Sometimes people take a car that starts off with a 9000 rpm redline, has an 11.5:1 compression ratio, and a 280* duration camshaft, and an aggressive naturally aspirated-esque timing curve and decide to supercharge it for more power. One such example is kleemann's kompressor for the SLK55 AMG (which already makes 400 hp in normally aspirated form from an 11:1 compression ratio motor). In this type of application, if you use a more conservative cam, and dial out all the overlap, and increase the power stroke, in combination with an already high 11:1 compression ratio and a healthy amount of boost pressure (7psi or above) you will end up with a motor that produces extremely high peak cylinder pressures and those intense pressures and heat may easily start off a chain reaction of pre-ignition and detonation and you will find that no matter how much you retard the timing that the setup will end up both powerless and still not that safe.

In this case, I would consider RPM and compression my primary power adder, and my supercharger as my secondary power adder (that is unless I decided to change that and went ahead and lowered the compression ratio of the motor). In this case it is ok to sacrifice some supercharger high rpm efficiency for preventing high-load & low-rpm detonation. Furthermore, to overcome the overlap inherent in this kind of high rpm normally aspirated power-plant it would be very advisable to use a centrifugal supercharger that is capable of producing more boost and flow with increased rpm rather than a roots type charger that will easily run out of boost and flow capacity (CFM) when facing an aggressive camshaft 'leaking' boost away.

Article Source: http://EzineArticles.com/2473412

Meercedes Kompressor cam profile to ponder
http://www.planetsupercar.com/forum/sho ... 791&page=1
http://www.execstudio.com/products_pack ... _power.htm
http://mbworld.org/forums/c32-amg-c55-a ... -cams.html

jseng1 · Apr 4, 2012

comnoz said:
First is the PW3 vs Js2 , they are nearly the same. The pw3 has a little more lift and the js2 has a little more overlap. I would expect similar performance.

The PW3 is a great cam, but performance is not the same between the JS2 and the PW3. There were two nearly identical Seeley bikes at Daytona - both had JS pistons/rods, full auto heads, same exhaust, carbs & ignition . But the faster bike had more port work by Jim C. Both were on the track at the same time and the Bike with the JS2 cam pulled away pulled away from the PW3 cam bike when power was applied (and took 1st place). True the ramps are similar but the JS2 has MORE DURATION and the lobe centers are closer together. The JS2 cam has 105 lobe centers and the PW3 has 107 lobe centers and that makes a noticeable difference in performance.

See another comparison of the JS2 cam to the PW3 made Jim Mosher when he built a 155 hps 920cc Nitros powered 920 for Fred Eiker (with JS 2 cam).

jseng1 · Apr 4, 2012

Deleted duplicate post

comnoz · Apr 4, 2012

jseng1 said:
comnoz said:

First is the PW3 vs Js2 , they are nearly the same. The pw3 has a little more lift and the js2 has a little more overlap. I would expect similar performance.

Click to expand...

The PW3 is a great cam, but performance is not the same between the JS2 and the PW3. You can ask Kenny Cummings about that. He rode two nearly identical Seeley bikes at Daytona - both had JS pistons/rods, full auto heads, same exhaust, carbs & ignition . Both were on the track at the same time and the Bike with the JS2 cam pulled away pulled away from the PW3 cam bike when power was applied (and took 1st place). True the ramps are similar but the JS2 has MORE DURATION and the lobe centers are closer together. The JS2 cam has 105 lobe centers and the PW3 has 107 lobe centers and that makes a noticeable difference in performance.

See another comparison of the JS2 cam to the PW3 made Jim Mosher when he built a 155 hps 920cc Nitros powered 920 for Fred Eiker (with JS 2 cam).

Bad comparison on the Sealeys. The faster Sealey had about 8 hours of port-work done on it along with your cam, the flow sheets for both heads are posted . Kenny's bike has a stock Fullauto head -although I do like the lighter followers. Jim

jseng1 · Apr 4, 2012

comnoz said:
jseng1 said:

comnoz said:

PW3 vs Js2 ,

Bad comparison. The faster Sealey had about 8 hours of port-work done on it along with your cam, the flow sheets for both heads are posted . Kenny's bike has a stock Fullauto head -although I do like the lighter followers. Jim

Click to expand...

Click to expand...

Then someone will have to test both cams with identical heads. I doubt if that will will happen. No one has to tell you the difference between the same cam lobes on two cams - but one with tighter lobe centers. Axtell sold his #3s with 105 L.C. for the street and 104 for the track. The hotter ones had 103 or 102 L.C. and you could really tell the difference between them.

comnoz · Apr 4, 2012

jseng1 said:
PW3 vs Js2 ,

Then someone will have to test both cams with identical heads. I doubt if that will will happen. No one has to tell you the difference between the same cam lobes on two cams - but one with tighter lobe centers. Axtell sold his #3s with 105 L.C. for the street and 104 for the track. The hotter ones had 103 or 102 L.C. and you could easily tell the difference between them.

A back to back test would be nice and easy however optimizing the intake and exhaust for one cam and then the other is a little tougher. An exact timing spec that works for one may not have the same results for another. Both cams are solid performers. I prefer your [JS] cam for the alloy used and the lightweight followers. Jim

And by the way comparing the JS2 to the PW3 was intended as a compliment. The PW3 has a long and well deserved reputation for working well on the roadrace circuit. I think the JS2 can also and not be as fragile.

Whitworth Ranch · Apr 4, 2012

I've got a perfectly nice running stock 850. I really don't need this kind of encouragement!

Great information here. On the "favorite" street grinds, how is spring and cam/lifter life? What about idle quality/low-rpm throttle response with new 932s and, say, a Tri Spark?
Mark

comnoz · Apr 4, 2012

Whitworth Ranch said:
I've got a perfectly nice running stock 850. I really don't need this kind of encouragement!

Great information here. On the "favorite" street grinds, how is spring and cam/lifter life? What about idle quality/low-rpm throttle response with new 932s and, say, a Tri Spark?
Mark

Mark,
The WC 12 is close to stock with a similar powerband and idle. Just a little more torque from 4 to 6000.

The 12a still idles happily and runs well but it will reduce the torque below 4500 and add some above that. Performance springs are needed. It needs extra compression and a tuned exhaust to work best. Valve to valve clearance needs to be watched. Often times you will need to sink the exhaust valve for clearance. It makes a great short track roadrace cam also. It is strongest from about 5 to 7000. Jim

nortriubuell · Apr 4, 2012

Wow ... though mostly over my head, great thread ya started here Jim !!! Just curious, I've got a 1971 750 motor, and the cam is marked "SS" :shock: Is this a hi performance Norton OEM cam ??? Perhaps i should use it in the 850 motor I'm building; opinions from all are invited ...

comnoz · Apr 4, 2012

nortriubuell said:
Wow ... though mostly over my head, great thread ya started here Jim !!! Just curious, I've got a 1971 750 motor, and the cam is marked "SS" :shock: Is this a hi performance Norton OEM cam ??? Perhaps i should use it in the 850 motor I'm building; opinions from all are invited ...

That sounds like a 2S- Combat cam. You can confirm that by measuring one intake and one exhaust lobe. They would be quite a bit different. The 2S cam is the only factory cam with considerably more lift on the intake than the exhaust. Jim

nortriubuell · Apr 5, 2012

comnoz said:
nortriubuell said:

Wow ... though mostly over my head, great thread ya started here Jim !!! Just curious, I've got a 1971 750 motor, and the cam is marked "SS" :shock: Is this a hi performance Norton OEM cam ??? Perhaps i should use it in the 850 motor I'm building; opinions from all are invited ...

Click to expand...

That sounds like a 2S- Combat cam. You can confirm that by measuring one intake and one exhaust lobe. They would be quite a bit different. The 2S cam is the only factory cam with considerably more lift on the intake than the exhaust. Jim

Well, your EXACTLY correct Jim. (still don't understand why Norton marked it "SS" ... but then "call" it a ... "2S" what kind of "pizzaro world" logic is that ??? :?

Anyway, it measures 1.263 and other is 1.261" for the the inner lobes; and measures 1.219" and 1.218" for the outer lobes. So the inner lobes are a bit larger as you say. Yes, quite different indeed.

It still puzzles me though, any thoughts on why Norton marked it "SS" ... but then call it a "2S" ??? :? BTW, this cam was in a 1974 850 motor I stripped :shock:

lcrken · Apr 5, 2012

comnoz said:
That sounds like a 2S- Combat cam. You can confirm that by measuring one intake and one exhaust lobe. They would be quite a bit different. The 2S cam is the only factory cam with considerably more lift on the intake than the exhaust. Jim

Jim, as I recall, the factory 3S and 4S cams also had that sort of design, much more intake lift than exhaust. Admittedly, standard Commandos didn't come with those cams, so if that's what you meant by factory cam, you're still correct. As far as I know, the 3S was only used in the Commando Production Racers, and the 4S only in the short stroke 750. And people are still arguing about whether any standard Commandos were really sold to the public with the short stroke engine. The 3S was never very well thought of as a cam, but the 4S has been pretty popular with racers, in spite of that .016" clearance spec.

Ken

comnoz · Apr 5, 2012

Ken,
That is true.
I have never seen a 3s or 4s that came in an engine from the factory so I figured a 2s was a safe bet.

I raced with a 4s for some time. I liked it partially because of the wide clearances. It was much more forgiving with aluminum barrels and steel pushrods. I even used one in my streetbike for a long time and wish it was still there..
I have never seen a 3s. Jim

Whitworth Ranch · Apr 5, 2012

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

comnoz · Apr 5, 2012

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

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

SteveA · Apr 6, 2012

As far as I know the 2S profile cam was derived from the earlier 650SS cam profile hence the SS stamping, and it was 'called' 2S after the later cams were called 3S and 4S. I guess it was only easy to stamp two characters on the cam!

The 4S cam profile was popular with UK racers as early as maybe 73 certainly 74, plenty of them in use in 75 when I started racing. So they were around when the only people in the UK with 750 short stroke engines were at Thruxton, so it may well have been used in 'production' short stroke bikes, but the design predates them, and may not have been designed for them.

The cam I ran from 76 to 79 was only marked TX, so you can guess where it came from, no, not Texas, it was a PW design that made about the same top end as a 4S but had more mid range.....like a train in an 850, even with a short stroke head and pistons and 34mm ports/36mm carbs....I suspect in reality it was was pretty close to a PW3....without the latter's refinements.....please don't ask where is it now....

Cams (2012)

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