PW3 cam for 850

Peter R · Jun 4, 2017

Hello, can any of you tell what will be the effect (positive and/or negative) of fitting a PW3 camshaft to an otherwise stock 850 ?

SteveA · Jun 4, 2017

Peter R said:
Hello, can any of you tell what will be the effect (positive and/or negative) of fitting a PW3 camshaft to an otherwise stock 850 ?

I am sure this has been discussed here many times before, try searching.

Without even thinking of performance and rideability, which will be OK if you set the package set up properly. It is a good cam design, often copied, manufacture may not be as good as some alternatives.

If you put in a PW3 it won't really be stock! You will need new followers to go with the cam, new timimg chain and tensioner, maybe timing gears and intermediate spindle, a good good oil pump, you will need to check for cam bush wear. You will have to check valve to piston clearance, and maybe pocket the pistons, you will need at the very least new standard springs, possibly new rockers spindles and valves depending on what you find, but you will need to check coil bind at full lift, and maybe shim the springs to get the correct spring pressures. Then when you have it running you will have to mess with jetting etc.

If you are doing all this work, stripping down to the last part, cleaning sludge trap, checking and maybe replacing shells, maybe a grank grind, replacing 40 year old rods, pistons/rings, why leave the rest stock if what you really want is increased performance?

Bear in mind that if you don't get the set up correct, it will probably disappoint.

What exactly do you feel is the limitation of the excellent standard cam? It is great for daily ride torque.

If your motor is down on power a good stock rebuild, and possibly new carbs/ignition will probably get you something easy to ride and enjoyable, with a whole lot less hassle.

toppy · Jun 4, 2017

You will probably need more compression to get the best from it (i did but my motor is not stock). Reassembling without base gasket an using JS Motorsport 0.003" head gasket replacement rings gave me 9 to 1 compression ratio as best i can measure but you will need valve pockets. If you just put a cam in to stock motor you won't get the best from it and your time an money may be better spent making sure your stock motor is as good as it can be. IMHO

gripper · Jun 4, 2017

The main issue will be, does the new cam clear the bottom of the cam follower (tappet) bore in the barrel and also the cam tunnel in the crank cases? Coil bound valve springs and valve to piston clearance is also an issue. 0.012" valve clearances mean it will be noisier also.

CanukNortonNut · Jun 4, 2017

Peter R said:
Hello, can any of you tell what will be the effect (positive and/or negative) of fitting a PW3 camshaft to an otherwise stock 850 ?

Peter,
You need to talk to Fullauto on this forum. He has his 850 set up with this cam shaft and will be able to tell you the hurtles that you need to cross to set your bike up. I would private message him. I am sure he will respond to your inquiries. Check out his rebuild here: fullauto-850-rebuild-t22547.html
Cheers,
Thomas

comnoz · Jun 4, 2017

The last time I did a PW3 in an otherwise stock motor the back to back dyno tests showed a loss of about 5 horse at 4500 and a gain of about 3 horse at 6500.

However the owner was thrilled by the rush between 4500 and 6500 and said he liked the extra power - no doubt due to the steep raise in power between those two points. Jim

Fullauto · Jun 4, 2017

comnoz said:
The last time I did a PW3 in an otherwise stock motor the back to back dyno tests showed a loss of about 5 horse at 4500 and a gain of about 3 horse at 6500.

However the owner was thrilled by the rush between 4500 and 6500 and said he liked the extra power - no doubt due to the steep raise in power between those two points. Jim

That's strange. I don't find that at all. When my bike had the PW3 fitted, the only thing changed was the addition of your excellent conical valve springs and the difference was significant, everywhere. I will copy and post what I wrote on another, ahem, forum.

I have had a PW3 fitted to my 73 MKI for 15,000 miles and 15 months now. The only other mods are a standard Fullauto Technologies cylinder head with conical valve springs and a single VM34 Mikuni. I have had the head on the bike for about 35,000 miles now. The difference in performance is astounding. Super torquey from zero revs.Very strong right through the mid range. As I limit my revs to 5000, I don't care what happens after this. but, I would imagine that the show continues into the top end, the only limiting factor being the single Mikuni, known to run out of puff at the top end of town.. It is an everyday bike for me. When the head was fitted to my bike it made it much stronger right through the rev range . The PW3 has added the same boost again. I run a 22 tooth sprocket but it is far stronger than a standard 850 on standard gearing. I used to run a 23 tooth when I lived in the country and did a lot of highway miles. I had the head fitted at that stage, but when you were cruising at 70mph and had to drop your speed back to say, 60 mph when you came up behind other vehicles, accelerating back up to 70mph was a bit leisurely. Now, acceleration between 50 to 70 mph, and beyond. is very impressive in top gear. It would pull a 23 tooth easily. I can't get my head around the fact that this was the factory race cam back in the day, as performance off idle is so strong! Dribbling along in traffic is not an issue. I hate any mods that move the power band further up the rev range as this goes against what the Norton provides. As it stands, I use less revs than a standard bike whilst accelerating more quickly, which has to be better for longevity. All with over 60mpg!

Do I like my PW3? I love it! Run off now to Andover Norton and buy one.

comnoz · Jun 4, 2017

There is no doubt the Fullauto head will increase the intake velocity and help overcome the loss from long intake duration. The fact that you are running a single carb will eliminate the top end rush.

Many times the seat of the pants dyno will fool you when the power curve is altered.

If it works for you then that is good but replacing a stock cam in a stock motor [w/RH4 head] did result in a shift in power to the higher rpm range.

I would stay with a stock or near stock cam in a stock motor, but you can get away with longer duration with small ports like in a Fullauto head. Jim

Fullauto said:
comnoz said:

The last time I did a PW3 in an otherwise stock motor the back to back dyno tests showed a loss of about 5 horse at 4500 and a gain of about 3 horse at 6500.

However the owner was thrilled by the rush between 4500 and 6500 and said he liked the extra power - no doubt due to the steep raise in power between those two points. Jim

Click to expand...

That's strange. I don't find that at all. When my bike had the PW3 fitted, the only thing changed was the addition of your excellent conical valve springs and the difference was significant, everywhere. I will copy and post what I wrote on another, ahem, forum.

I have had a PW3 fitted to my 73 MKI for 15,000 miles and 15 months now. The only other mods are a standard Fullauto Technologies cylinder head with conical valve springs and a single VM34 Mikuni. I have had the head on the bike for about 35,000 miles now. The difference in performance is astounding. Super torquey from zero revs.Very strong right through the mid range. As I limit my revs to 5000, I don't care what happens after this. but, I would imagine that the show continues into the top end, the only limiting factor being the single Mikuni, known to run out of puff at the top end of town.. It is an everyday bike for me. When the head was fitted to my bike it made it much stronger right through the rev range . The PW3 has added the same boost again. I run a 22 tooth sprocket but it is far stronger than a standard 850 on standard gearing. I used to run a 23 tooth when I lived in the country and did a lot of highway miles. I had the head fitted at that stage, but when you were cruising at 70mph and had to drop your speed back to say, 60 mph when you came up behind other vehicles, accelerating back up to 70mph was a bit leisurely. Now, acceleration between 50 to 70 mph, and beyond. is very impressive in top gear. It would pull a 23 tooth easily. I can't get my head around the fact that this was the factory race cam back in the day, as performance off idle is so strong! Dribbling along in traffic is not an issue. I hate any mods that move the power band further up the rev range as this goes against what the Norton provides. As it stands, I use less revs than a standard bike whilst accelerating more quickly, which has to be better for longevity. All with over 60mpg!

Do I like my PW3? I love it! Run off now to Andover Norton and buy one.

Fullauto · Jun 5, 2017

So, Jim, what you are saying is that everybody should have a Fullauto Technologies head?

gortnipper · Jun 5, 2017

cams-t12813.html

dobba99 · Jun 5, 2017

Hello Peter
Unless you are prepared to do a lot of additional work (covered in the previous replies) it is not worth the hassle fitting a performance cam in one of these engines. Higher lift, duration etc will wear the valve gear out sooner. Jims dyno test reveals that you lose in the midrange for a 3 horse gain at the top end.
ask yourself this question:-
Do you ride everywhere at wide open throttle?
you will get an increase in noise though!

A little bit of background to the PW3. designed by the great Peter Williams, the promotion of these cams as being the best one to fit in these engines is because of the two gentlemen responsible for getting a batch of them made will tell you that!
It is in their interest to push these cams onto customers where really it is not in the best interest of said customer.
Essentially it is a cam designed for racing. Which is fine if that is what you are going to do (chase every last bit of horsepower)
For road use, rideability and longevity of your engine stick to the standard cam.
At the end of the day it is your money and you can do anything.
Just my five pence worth.
regards
Peter

Fullauto · Jun 5, 2017

dobba99 said:
Hello Peter
Unless you are prepared to do a lot of additional work (covered in the previous replies) it is not worth the hassle fitting a performance cam in one of these engines. Higher lift, duration etc will wear the valve gear out sooner. Jims dyno test reveals that you lose in the midrange for a 3 horse gain at the top end.
ask yourself this question:-
Do you ride everywhere at wide open throttle?
you will get an increase in noise though!

A little bit of background to the PW3. designed by the great Peter Williams, the promotion of these cams as being the best one to fit in these engines is because of the two gentlemen responsible for getting a batch of them made will tell you that!
It is in their interest to push these cams onto customers where really it is not in the best interest of said customer.
Essentially it is a cam designed for racing. Which is fine if that is what you are going to do (chase every last bit of horsepower)
For road use, rideability and longevity of your engine stick to the standard cam.
At the end of the day it is your money and you can do anything.
Just my five pence worth.
regards
Peter

I don't have any commercial axe to grind. You are implying bias on the part of two people in the industry for profit. Nice inference. I, on the other hand, have no commercial interest in the PW3 cam. I bought one and had it fitted. It works incredibly well. For me and my particular engine in its build specs. My engine is stock in almost all respects. Like I said. One of my cylinder heads, Jim's conical valve springs and the PW3. I had a direct comparison when I crashed it and it had a rebuild out of that incident. I can tell you, despite it being a seat of the pants impression, that this combination provides strong performance from 0 to 5000 rpm. This is the range where the Norton motor produces the goods. A top endy motor in a Norton is an exercise in futility. You are not playing to the Norton's strengths, which are its smooth, torquey performance in the low end and the mid range. This combination absolutely provides power everywhere, with a motor that doesn't require you to rev it as hard as a standard motor to do a better job. I put enough miles on it in many different circumstances to confirm my findings. Anybody is welcome to ride my bike.

I'll be having it dynoed shortly against a standard spec 850 on the same day, so, we shall see.

dobba99 · Jun 5, 2017

Fullauto said:
dobba99 said:

Hello Peter
Unless you are prepared to do a lot of additional work (covered in the previous replies) it is not worth the hassle fitting a performance cam in one of these engines. Higher lift, duration etc will wear the valve gear out sooner. Jims dyno test reveals that you lose in the midrange for a 3 horse gain at the top end.
ask yourself this question:-
Do you ride everywhere at wide open throttle?
you will get an increase in noise though!

A little bit of background to the PW3. designed by the great Peter Williams, the promotion of these cams as being the best one to fit in these engines is because of the two gentlemen responsible for getting a batch of them made will tell you that!
It is in their interest to push these cams onto customers where really it is not in the best interest of said customer.
Essentially it is a cam designed for racing. Which is fine if that is what you are going to do (chase every last bit of horsepower)
For road use, rideability and longevity of your engine stick to the standard cam.
At the end of the day it is your money and you can do anything.
Just my five pence worth.
regards
Peter

Click to expand...

I don't have any commercial axe to grind. You are implying bias on the part of two people in the industry for profit. Nice inference. I, on the other hand, have no commercial interest in the PW3 cam. I bought one and had it fitted. It works incredibly well. For me and my particular engine in its build specs. My engine is stock in almost all respects. Like I said. One of my cylinder heads, Jim's conical valve springs and the PW3. I had a direct comparison when I crashed it and it had a rebuild out of that incident. I can tell you, despite it being a seat of the pants impression, that this combination provides strong performance from 0 to 5000 rpm. This is the range where the Norton motor produces the goods. A top endy motor in a Norton is an exercise in futility. You are not playing to the Norton's strengths, which are its smooth, torquey performance in the low end and the mid range. This combination absolutely provides power everywhere, with a motor that doesn't require you to rev it as hard as a standard motor to do a better job. I put enough miles on it in many different circumstances to confirm my findings. Anybody is welcome to ride my bike.

I'll be having it dynoed shortly against a standard spec 850 on the same day, so, we shall see.

I dont have any commercial axe to grind either. i am not implying bias, just quoting facts.
I had a chap contact me late last year, asking me if i could sort out his non starting electric start MK3. I said yes if he could get the bike to me. Further along in the first telephone conversation with him he said that he was new to Nortons and that he had had the engine rebuilt by one of the two gentlemen mentioned. I immediately interrupted him saying 'don't tell me, he fitted a PW3 cam in it'
'HOW DO YOU KNOW THAT?' he said. 'I don't know what a PW3 cam is and i definitely didn't ask for one fitting'.

A month or so later i was relating this tale to the chairman of one our Local NOC
'Mnnn that sounds a bit familiar' he said.
'I rang up the other gentleman mentioned and got his wife on the phone taking his order. When he said could you please send me a standard cam the gentleman shouted across the room' (it must have been on speakerphone) 'he wants a PW3'
He had to insist that they send him a standard cam.

PM me if you want the names of the two gentlemen concerned though i think you know them already
Regards
Peter

Fullauto · Jun 5, 2017

No need to name names. It's pretty clear who you are talking about. But stating that "it is in their best interests" is NOT stating facts, it is an implication that these people have sold a product "not suitable for purpose". So, ultimately, IN YOUR OPINION, the PW3 is not worth the money. Why didn't you just state that and leave it at that?

IN MY OPINION, the PW3 has given me a significant power boost across the range, with my minimal engine work. I'm sticking to it.

Holmeslice · Jun 5, 2017

Fullauto said:
No need to name names. It's pretty clear who you are talking about. But stating that "it is in their best interests" is NOT stating facts, it is an implication that these people have sold a product "not suitable for purpose". So, ultimately, IN YOUR OPINION, the PW3 is not worth the money. Why didn't you just state that and leave it at that?

IN MY OPINION, the PW3 has given me a significant power boost across the range, with my minimal engine work. I'm sticking to it.

We have fitted PW3 cams to many bikes - from my own multi-championship winning Commando racer (and others) to several performance street bikes (750s and 850s) that come out of NYC Norton. I agree with Comnoz - the PW3 can rob from the low mid for the benefit of the top, but if this is done in concert with other tuning aspects such as a Fullauto head (or some serious headwork to get close to a Fullauto) then it is an absolute hoot to have. But fitting any high lift cam into a Commando requires more than just dropping it in. The cases need to be opened to fit the cam lobes, the lifter tunnels must be machined down to clear. If going with a PW3 in an 850 the valves will get very close to the flat top pistons (or even hit), so this must be considered. Then we get to exhaust tuning, etc. But if you are planning on fitting a high lift cam and not doing some serious blueprinting work anyway, then this is all a loss. There are other mild performance cams out there that might be an easier fit for a street bike, and these should definitely be considered as well.

Now, I think I know who this unnamed vendor is mentioned in this thread, and I will say in my not so humble opinion they are quite possibly the best Norton folks around, and in my many years of dealing with them have never experienced them pushing something that was "convenient" to their bottom line at the detriment to the end user. Their reputation speaks for itself.

-Kenny Cummings

comnoz · Jun 5, 2017

Fullauto said:
So, Jim, what you are saying is that everybody should have a Fullauto Technologies head?

Well of course they should.

Fitting a large cam to an engine equipped with a Fullauto head is quite a bit different than fitting a large cam to stock engine. There are large differences in the port flow velocities. Jim

SteveA · Jun 5, 2017

Holmeslice said:
Now, I think I know who this unnamed vendor is mentioned in this thread, and I will say in my not so humble opinion they are quite possibly the best Norton folks around, and in my many years of dealing with them have never experienced them pushing something that was "convenient" to their bottom line at the detriment to the end user. Their reputation speaks for itself.

-Kenny Cummings

There are two unamed vendors in the earlier, I agree fully with your comments, and I would say it applies to both of them.

When I made my comments about the work needed to fit the cam I forgot add the cam follower tunnel clearance requirement. When I did my build with a PW3 the barrels I used needed a rebore and my spare set needed sleeving, one of the unamed vendors automatically did the cam clearance work to both sets of barrels without my needing to ask. I would deal with either of them again tomorrow when the need arises.

One of them also sold me a Fullauto head 8)

acotrel · Jun 5, 2017

Before you fit the Fullauto head and the PW3 cam, have you done as much as you can with what you have got ? If you haven't got the gearbox, you have not got the bike. Moving the power band up the rev range is not always the best answer to the problem of going faster on a Commando. Everything becomes more expensive.

Robert_Norton · Jun 5, 2017

Peter R said:
Hello, can any of you tell what will be the effect (positive and/or negative) of fitting a PW3 camshaft to an otherwise stock 850 ?

Peter R,

There are a number of videos, posted by Jim Comstock on youtube, who is the member here known as "comnoz," that demonstrate the valve action(s) with various cams at different RPM'S. Draw your own conclusions by watching these two videos:

https://www.youtube.com/watch?v=L0_pud6vcuw

https://www.youtube.com/watch?v=5M_OrQlYkWE

Peruse through his youtube channel and you'll find additional cams being demonstrated, too.

And as previously suggested, read through this thread for more information: cams-t12813.html

Note that Jim Comstock is a Webcam dealer. His website is http://www.nortonmachineshop.com/. In my opinion, anyone on this board who buys a Webcam cam for a Norton, should be buying it from him -- in appreciation for the immense amount of knowledge he has selflessly imparted to all Norton Commando enthusiasts.

.

Fullauto · Jun 5, 2017

comnoz said:
Fullauto said:

So, Jim, what you are saying is that everybody should have a Fullauto Technologies head?

Click to expand...

Well of course they should.

Fitting a large cam to an engine equipped with a Fullauto head is quite a bit different than fitting a large cam to stock engine. There are large differences in the port flow velocities. Jim

You are truly the eighth wonder of the world! You should have a full volume of the Encyclopedia Brittanica dedicated to your work. Thank you, as always, for providing your insight. I certainly learned something.