PW3 Camshaft

Fast Eddie · Nov 18, 2016

Fullauto said:
Fast Eddie said:

I once rode an 850 with a single Mikuni (forgot the size), Ham-can filter, peashooters, PW3 cam, and stock CR.

Below 5k it was gutless, above 5k it just wheezed breathlessly. It had neither the bottom end torque nor the top end pull that Commandos are famous for! It was awful.

Being a MK3, it had a RH4 head.

I can only assume Ken that your FA head compliments the PW3 and vice versa, in some way that 'works'. It seems the only significant difference between your bike and the one that I rode, but your description of your bikes performance bears no resemblance at all to the one I rode!

Click to expand...

Who built it?

A well known U.K. Norton expert. Don't wanna be any more specific than that...

comnoz · Nov 19, 2016

worntorn said:
I don't think it's likely that a hot cam will make the powerband stronger everywhere, nor is it going to make an engine stronger low down in the powerband. Just the opposite.
Phil Irving covers this stuff very well in "Tuning for Speed" He explains why a high lift big overlap can loses power down low and improves power at top, essentially moving the powerband up.

He would sometimes custom grind "RV" cams for his close friends. He did this for various makes of bikes. If someone wanted bike for two up mountain touring or sidecar work, these came were ideal. He started with mild stock street cams then reground them for less overlap, more pulling power.
The engine would lose some top RPM power, but the owners didn't mind as they never went there anyway.

Glen

If an engine is optimized, meaning the cam, compression, porting, pipes, timing, fuel and anything else that may change the tune of the engine are at the optimum specification to make maximum power in it's intended rpm range -then a change to a cam with more duration while making no other changes, will always move the powerband upwards.
It will produce less power below some point and more power above that point than it did before.

There are a lot of variables that may make this not happen as predicted. If something was not "optimized" before the cam change then the new cam may tune better with what was there and make more power at a lower rpm.

It's also well known that a new camshaft along with the correct pipes, compression, carb, fuel, ect may make more power throughout the range -but the maximum power will generally occur at a higher rpm than it did before.

It is very easy to install too large a cam in a Norton and end up with an engine that runs nice and smooth but never comes "on the pipe". In other words, by the time the engine reaches the rpm where the cam would be in it's efficient operating range then it is beyond the operating range of other components, and the resulting powerband is very flat. The dyno chart will not show the pronounced bump that you get when things "come into tune" with one another. Jim

Fullauto · Nov 19, 2016

Fast Eddie said:
Fullauto said:

Fast Eddie said:

I once rode an 850 with a single Mikuni (forgot the size), Ham-can filter, peashooters, PW3 cam, and stock CR.

Below 5k it was gutless, above 5k it just wheezed breathlessly. It had neither the bottom end torque nor the top end pull that Commandos are famous for! It was awful.

Being a MK3, it had a RH4 head.

I can only assume Ken that your FA head compliments the PW3 and vice versa, in some way that 'works'. It seems the only significant difference between your bike and the one that I rode, but your description of your bikes performance bears no resemblance at all to the one I rode!

Click to expand...

Who built it?

Click to expand...

A well known U.K. Norton expert. Don't wanna be any more specific than that...

What can I say, Nigel? I can only tell it like I see it and that is what I have found with my setup. It really is an eye opener.

johnny Lagdon · Nov 19, 2016

I have a 850 MK3 The engine has PW3 cam, Maney alloy barrels and pistons, gas flowed head withoversize inlet and exhaust valves opened by polished lighted rockers and fed by 35mm Keihin FCR flat slides sparked by a Pazon ignition. I find it very tractable and docile at low revs around town, and really gets up and goes when you give it some welly. Best of both worlds

worntorn · Nov 19, 2016

comnoz said:
If an engine is optimized, meaning the cam, compression, porting, pipes, timing, fuel and anything else that may change the tune of the engine are at the optimum specification to make maximum power in it's intended rpm range -then a change to a cam with more duration while making no other changes, will always move the powerband upwards.
It will produce less power below some point and more power above that point than it did before.

There are a lot of variables that may make this not happen as predicted. If something was not "optimized" before the cam change then the new cam may tune better with what was there and make more power at a lower rpm.

It's also well known that a new camshaft along with the correct pipes, compression, carb, fuel, ect may make more power throughout the range -but the maximum power will generally occur at a higher rpm than it did before.

It is very easy to install too large a cam in a Norton and end up with an engine that runs nice and smooth but never comes "on the pipe". In other words, by the time the engine reaches the rpm where the cam would be in it's efficient operating range then it is beyond the operating range of other components, and the resulting powerband is very flat. The dyno chart will not show the pronounced bump that you get when things "come into tune" with one another. Jim

This agrees with what I've observed with other makes and what Phil Irving says in the Speed Bible.

Mods like Johnny describes above would seem a great combo, especially if there is a little compression bump included.
Very similar to Nigel's 850.

When I was building the engine for my Special, our local motorcycle machinist whiz Dan Smith gave me some advice re Terry Prince high performance parts- " Put everything in, not just part of the kit. Back in the 70s lots of guys tried to hop up their Commandos by putting in part of a Dunstall kit. The whole kit made the bike fly, a part kit made it into a dog"
I put the whole kit in!

Glen

acotrel · Nov 20, 2016

worntorn said:
I don't think it's likely that a hot cam will make the powerband stronger everywhere, nor is it going to make an engine stronger low down in the powerband. Just the opposite.
Phil Irving covers this stuff very well in "Tuning for Speed" He explains why a high lift big overlap can loses power down low and improves power at top, essentially moving the powerband up.

He would sometimes custom grind "RV" cams for his close friends. He did this for various makes of bikes. If someone wanted bike for two up mountain touring or sidecar work, these came were ideal. He started with mild stock street cams then reground them for less overlap, more pulling power.
The engine would lose some top RPM power, but the owners didn't mind as they never went there anyway.

Glen

If the exhaust system has silencers, the restriction can smooth out most of any 8-stroking caused by a hot cam. The result is more power both below and above the cam spot. However you would not normally try to ride a bike with a hot cam slowly anyway

PW3 Camshaft

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