2S cam hits Cam follower (tappet) guide in barrels

Hi All, 1971 Commando. Has anyone noticed that the 2S cam hits the cam follower housing area of the barrels? Is grinding back the lower and of the barrels at that point a known requirement when fitting a 2S cam or have I just got barrels where lack of QC in 1971 played it's part in not machining these barrels enough.
Any experience or views appreciated.

ratbag said:

Hi All, 1971 Commando. Has anyone noticed that the 2S cam hits the cam follower housing area of the barrels? Is grinding back the lower and of the barrels at that point a known requirement when fitting a 2S cam or have I just got barrels where lack of QC in 1971 played it's part in not machining these barrels enough.
Any experience or views appreciated.

Click to expand...

Yes the clearance requirements changed for a 2S. The clearance mod is known for over 40 years.
combat cam with early 28.5mm heads is very nice...IMO
remove the insulation washers from the intakes...
Make sure you have late pistons that can tolerate the increased revs.... :mrgreen:

Mick Hemmings stated that you need to check for clearance issues with performance cams in his rebuild videos. Remove the material. It's not a lack of QC.
If you are using the 2S cam then you should be getting the compression ratio up from the stock 71 ratio. This cam works best when you are running 10:1
Tom
CNN

CanukNortonNut said:

Mick Hemmings stated that you need to check for clearance issues with performance cams in his rebuild videos. Remove the material. It's not a lack of QC.
If you are using the 2S cam then you should be getting the compression ratio up from the stock 71 ratio. This cam works best when you are running 10:1
Tom
CNN

Click to expand...

Theory... actually this i not quite true (IMO) per dyno resutls at the 1992 INOA rally...
My "combat with early 28.5 mm head" out performed all stock bikes including other combats. per Leo Geoff IDBA norton record holder.
When I finally put the rebuilt "combat" head (hi compression) it never ran as strong....
Small port flow velocity seemed to win out over the small compression boost of a combat head w/big ports.
But we are only talking 3-4 hp MAX.

dynodave said:

CanukNortonNut said:

Mick Hemmings stated that you need to check for clearance issues with performance cams in his rebuild videos. Remove the material. It's not a lack of QC.
If you are using the 2S cam then you should be getting the compression ratio up from the stock 71 ratio. This cam works best when you are running 10:1
Tom
CNN

Click to expand...

Theory... actually this i not quite true (IMO) per dyno resutls at the 1992 INOA rally...
My "combat with early 28.5 mm head" out performed all stock bikes including other combats. per Leo Geoff IDBA norton record holder.
When I finally put the rebuilt "combat" head (hi compression) it never ran as strong....
Small port flow velocity seemed to win out over the small compression boost of a combat head w/big ports.
But we are only talking 3-4 hp MAX.

Click to expand...

Small port flow velocity seemed to win out over the small compression boost of a combat head w/big ports.
But we are only talking 3-4 hp MAX.[/quote]

True statement with that Dave. I will not argue that. 32 mm ports was not the way to go for a road bike. The 2S needs compression to work.

dynodave said:

CanukNortonNut said:

Mick Hemmings stated that you need to check for clearance issues with performance cams in his rebuild videos. Remove the material. It's not a lack of QC.
If you are using the 2S cam then you should be getting the compression ratio up from the stock 71 ratio. This cam works best when you are running 10:1
Tom
CNN

Click to expand...

Theory... actually this i not quite true (IMO) per dyno resutls at the 1992 INOA rally...
My "combat with early 28.5 mm head" out performed all stock bikes including other combats. per Leo Geoff IDBA norton record holder.
When I finally put the rebuilt "combat" head (hi compression) it never ran as strong....
Small port flow velocity seemed to win out over the small compression boost of a combat head w/big ports.
But we are only talking 3-4 hp MAX.

Click to expand...

It has been my feeling that since I swapped out my tired Combat head for the RH1, it has been a stronger bike. I had Comnoz do the guides and set the valves. I shaved it .040" and the only thing I did to the intake ports is to flare them to meet the 32mm manifolds. I went in 1/2".

JS1 and beehive stuff.
Have we gone off topic?

Hehe Dyno tested against some pretty expensive fancied up engine completion. Just shy of 50 rwhp. All of Ms Peel peak power daze was with 28.5 mm ports unshaved with 2S cam so next time thinking put on Trixie with more pleasing effect by leaving the .040" gasket out and shorten push rods. Peel flat poopoo'd out with 2 new dialed in Amals and Combat head with Deer k/w 7mm valve kit - ugh. I did find out the Combat head does flow well after red zone rpm ugh.

I'm wondering about the comment that the 2S cam needs compression to work properly . I've used a lot of different race cams in various motors, however I've never noticed that relationship. E3134 Triumph race cams exhibit the same power band characteristics whether used at 7 to 1 or 12 to 1 comp. , if nothing else is changed. Why would a road cam such as the 2S behave differently ? The higher compression adds a bit more power right across the rev range, however why is that necessary or desirable ?

acotrel said:

I'm wondering about the comment that the 2S cam needs compression to work properly . I've used a lot of different race cams in various motors, however I've never noticed that relationship. E3134 Triumph race cams exhibit the same power band characteristics whether used at 7 to 1 or 12 to 1 comp. , if nothing else is changed. Why would a road cam such as the 2S behave differently ? The higher compression adds a bit more power right across the rev range, however why is that necessary or desirable ?

Click to expand...

Don't quote me on this, and I hope people will expound on my thinking, but i think it has something to do with hemipherical combustion chamber and the timing which is much less the the Thiumph.

It just seems that I heard this somewhere.
Sorry to be imcomplete.

for public use just needs enough CR to start and idle w/o having to blip like a dragster waiting to launch. May not 'come on cam' as ealier but still should before redline. There's a few percentage mo h-pow with higher CR + octane so what racer would leave that on the table is all.

http://victorylibrary.com/brit/compression-c.htm
stock 750 approx 9:1 (8.9)
combat 10:1
+ 3.6% from CR
cam alone gives you more than that. maybe 6% just guessing
I know of several low comp 850's that run 2S cams seem to run fine as a street bike, though not a killer hot rod either.

dynodave said:

CanukNortonNut said:

Mick Hemmings stated that you need to check for clearance issues with performance cams in his rebuild videos. Remove the material. It's not a lack of QC.
If you are using the 2S cam then you should be getting the compression ratio up from the stock 71 ratio. This cam works best when you are running 10:1
Tom
CNN

Click to expand...

Theory... actually this i not quite true (IMO) per dyno resutls at the 1992 INOA rally...
My "combat with early 28.5 mm head" out performed all stock bikes including other combats. per Leo Geoff IDBA norton record holder.
When I finally put the rebuilt "combat" head (hi compression) it never ran as strong....
Small port flow velocity seemed to win out over the small compression boost of a combat head w/big ports.
But we are only talking 3-4 hp MAX.

Click to expand...

Good to know if mine ever gets going, JS high comp pistons and a PW3 cam with the standard small port head

pete.v said:

acotrel said:

I'm wondering about the comment that the 2S cam needs compression to work properly . I've used a lot of different race cams in various motors, however I've never noticed that relationship. E3134 Triumph race cams exhibit the same power band characteristics whether used at 7 to 1 or 12 to 1 comp. , if nothing else is changed. Why would a road cam such as the 2S behave differently ? The higher compression adds a bit more power right across the rev range, however why is that necessary or desirable ?

Click to expand...

Don't quote me on this, and I hope people will expound on my thinking, but i think it has something to do with hemipherical combustion chamber and the timing which is much less the the Thiumph.

It just seems that I heard this somewhere.
Sorry to be imcomplete.

Click to expand...

It could explain why I believe what I get from my 850 cam is unusual. I know the Triumph chambers were always coked up on the side away from the plugs. I'm under the impression that the commando head is an all-round better design. I believe most of the older racer Triumphs are now dead or it would be worth making a commando style head for them. In any case it would be pretty impossible to get them up to the same capacity.

Cheesy said:

dynodave said:

CanukNortonNut said:

Mick Hemmings stated that you need to check for clearance issues with performance cams in his rebuild videos. Remove the material. It's not a lack of QC.
If you are using the 2S cam then you should be getting the compression ratio up from the stock 71 ratio. This cam works best when you are running 10:1
Tom
CNN

Click to expand...

Theory... actually this i not quite true (IMO) per dyno resutls at the 1992 INOA rally...
My "combat with early 28.5 mm head" out performed all stock bikes including other combats. per Leo Geoff IDBA norton record holder.
When I finally put the rebuilt "combat" head (hi compression) it never ran as strong....
Small port flow velocity seemed to win out over the small compression boost of a combat head w/big ports.
But we are only talking 3-4 hp MAX.

Click to expand...

Good to know if mine ever gets going, JS high comp pistons and a PW3 cam with the standard small port head

Click to expand...

I am a compression junkie and love to use HC pistons instead of screamer cams. However the requirement to have a different advance curve FAR exceeds the brit bike ignition offerings of todays market.
My phylosophy on nortons is to make as much high compression broad torque over peaky cam derived power. How ever this is a work in progress and no firm data is forthcoming.
The basis for this view is my experimental 73 chevy PU, where the dealer said "you will never see 10MPG with this truck". 8.5-9 was typical in the 70's
RV cam, HC pistons (11.5:1)(210-225PSI), headers and lots of ignition curve work, I got just over 17mpg from a 4000lb- gas- automatic truck. OH yeah...87/89 octane fuel.
School continues now on my norton. Though it will be built to use commonly available Premium USA octane ??? 91 ?? not 87

I am a compression junkie and love to use HC pistons instead of screamer cams. However the requirement to have a different advance curve FAR exceeds the brit bike ignition offerings of todays market.
My phylosophy on nortons is to make as much high compression broad torque over peaky cam derived power. How ever this is a work in progress and no firm data is forthcoming.
The basis for this view is my experimental 73 chevy PU, where the dealer said "you will never see 10MPG with this truck". 8.5-9 was typical in the 70's
RV cam, HC pistons (11.5:1)(210-225PSI), headers and lots of ignition curve work, I got just over 17mpg from a 4000lb- gas- automatic truck. OH yeah...87/89 octane fuel.
School continues now on my norton. Though it will be built to use commonly available Premium USA octane ??? 91 ?? not 87[/quote]

Thats interesting with the Chev, Im trying to get a range rover with a 4.5L stroker motor up and running. The initial ignition map I used feed in the advance really early and fast, even without sorting the fuel map (I did make sure it wasnt going lean though) the thing would squeak the tires on seal. I got a bit nervous and pulled some of the timing back until I get a round to tuning it properly (buying a wideband O2 sensor) and it has definitely lost a lot of power. I actually have another EFI unit that I was planning on using on the Norton. The one thing you notice straight away with the ignition (36-1 trigger wheel) on the rangy is how rock steady the timing is when using the timing light compared to the original electronic distributor setup

I am a compression junkie and love to use HC pistons instead of screamer cams. However the requirement to have a different advance curve FAR exceeds the brit bike ignition offerings of todays market.
My phylosophy on nortons is to make as much high compression broad torque over peaky cam derived power. How ever this is a work in progress and no firm data is forthcoming.
The basis for this view is my experimental 73 chevy PU, where the dealer said "you will never see 10MPG with this truck". 8.5-9 was typical in the 70's
RV cam, HC pistons (11.5:1)(210-225PSI), headers and lots of ignition curve work, I got just over 17mpg from a 4000lb- gas- automatic truck. OH yeah...87/89 octane fuel.
School continues now on my norton. Though it will be built to use commonly available Premium USA octane ??? 91 ?? not 87

Click to expand...

Re" However the requirement to have a different advance curve FAR exceeds the brit bike ignition offerings of todays market. "
This may be true of the modern ignition systems but not on my trusty old K2F magneto with manual advance retard that is operated by a cable via the handlebar.
I can set the advance almost anywhere that suits the engine, and if you are wondering how I would know if the advance is correct, you can feel as you ride along if it is right or not.

' how I would know if the advance is correct, you can feel as you ride along if it is right or not.'

You are a man after my own heart.