Cams (2012)

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Maybe ole caveman dynodave ain't selling his stock - he don't want the alien technology evolution appearing in one engine getting out to mis-used by the powers that be. If not for Dave Ms Peel would never been a has been.
 
dynodave said:
These are mostly engineering research and training samples from 1949-1975 with almost every norton heavy twin variant except a 650SS
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Well thats certainly an interesting revelation, and project.

Your website though says (?) that the early dommie alloy heads are the same casting as the old iron heads.
Careful examination would show that the alloy heads have slightly more finning than any iron heads, so that detail isn't correct ?
This was pointed out on the Model 7 forum too, we recall...
 
Rohan scine '99 I've been taken underwing of many well know living and late Nortoneers and Dyno and I have been very intimate on various Peel parts and isssues he discovered or solved by his services or takening parts off one of his Commandos to give to Peel and me. Dyno honored me by gifting one of his first clutch rod seals and one of the very few crank adaptor mounts for degree wheel. DynoDave is also one the few that's familar with Drouins so another area he's helped that don't get posted in forums. Take closer look at the heads lined up in his window display. Dave has congential eye lens fault so needs coke bottle thick glasses and bright light to see well but floored me on his nano level detection of fractures in alloy grains others need dye stain methods to detect before failure. Dave and Canaga advised how to repair this and UK-NOC and British Iron email crowd advised me on severe black smith methods to get cases to seal again.

Cams (2012)
 
After a few question I though I would graph my favorite street cams.

Here is the cam I use the most. It is a webcam #312 grind. It is a good drop in replacement in a stock or mildly modified engine. It makes a little more torque through the midrange due to the higher lift and it is smooth and easy to live with because of the reduced overlap. Idle and low speed performance is better than a standard Commando cam.

Here it is compared to the standard cam.

Cams (2012)


The next step up is the #312A grind run with 4 inch radius lifters. it has duration numbers slightly longer a stock cam with considerably more lift and a little more overlap than the stock cam. It likes a 9.5 to 1 compression ratio and works well with the stock exhaust. It is the setup that is in my bike now.

Cams (2012)


Then we get to the hot street grind. It is the same #312A but with flat lifters. An increase in duration and overlap make it come alive over 4500 rpm. It likes compression between 9.5 and 10-1. With the extra overlap -it responds well to exhaust tuning.
This was also the cam that I used with best results on the shorter roadrace courses. It revs freely and has a fairly wide powerband.

Cams (2012)


Here is the webcam #318A. It is equivalent to the #312A but designed for BSA followers. This is the two cams compared.

Cams (2012)
 
Does not compute to me comnoz, why spend all the spin faster effort to put a tractor low rpm cam in sheeze. I had seen 3 WAY OVER cammed cycles, i rode * time slip raced against 1 or em, 1200 wheelie barred drag only Sportser, that on hwy would lug and buck till like 4500+ then jerk your teeth out, for a short run up then hit it again, or would bog again. Hehe my 1st piece of shit clapped out loose as a goose sloppy pre-peel Combat got the jump on him and led him to top of 2nd and good way through 3rd mid 80s mph before out horse powered 1/8 m tract. Accidental Ms Peel was better enough than the Sportster to earn her name and as rider season here again locals telling the out of state elite riders asking about the Norton Nut. So please set me straighter on why i so poopped here yet have gun slinger show down reputation with just 3 seasons of exposure??? Very heady addicting high times I will never forget but want more so below is my current reasoning I would think other G force addicts might follow. Oh Yeah the other two OVER Cam bikes were a Laverda SFC 750 special one off extreme that was just nasty to here idle about to die between ear gut grinding blip up and almost spin outs trying to mover around off tarmac. Yet my P!! could eat all the above by 3rd gear yet hand off idle at 600 rpm lugging in 4th through tire deep sugar sand at 12 mph throwing the sand like boat wake but just a smooth roll on would instantly turn into a sand dune rooster tail throwing screamer to leap a bit over crest then settle back down to sight seeing speed in deep Fla. woods. This was the oldest school route so why is it not more common now a days?

Cams (2012)


I had to do a LOT of cogitating on Peel cam d/t the extremes she is intended for which realistically is fairly slow engine speeds on fairly high throttle, ie: just above lugging/chugging in and out of isolastion rpms on loose sloped surfaces which I get so scared of I routinely brake hard down to survive speeds for most blind crests and turns then instantly bore seeing way clear so nearly WOT back to curise or above, so after seeing some pretty hi strung vinteage cammed twin behaving like ordinary streer bikes in pits and yellow flag track operation, it made best since to get cam that was fairly whimmpy bit lumpy idle bangy idle d/t the early exht opening for normal sane mild throttle operation yet with just a bit of delay in taller gear it wakes up nicely to pull great or just a snick or two down for a struggle to hang on vs letting off for hook up. Ahhhhh, I had this twice so far on two Nortons so hope adding them together will blow me away.
 
Why?
Because it is a tractor motor.

Why cam a longstroke motor to tune best at an RPM range that is beyond its normally used rpm?



By the way- a Duntov Corvette cam runs around 230 degrees of duration at .050 lift. Now there is a real tractor motor... :D

A stock Commando cam runs around 250 degrees duration at .050. Jim
 
hobot said:
Does not compute to me comnoz, why spend all the spin faster effort to put a tractor low rpm cam in sheeze. I had seen 3 WAY OVER cammed cycles, i rode * time slip raced against 1 or em, 1200 wheelie barred drag only Sportser, that on hwy would lug and buck till like 4500+ then jerk your teeth out, for a short run up then hit it again, or would bog again. Hehe my 1st piece of shit clapped out loose as a goose sloppy pre-peel Combat got the jump on him and led him to top of 2nd and good way through 3rd mid 80s mph before out horse powered 1/8 m tract. Accidental Ms Peel was better enough than the Sportster to earn her name and as rider season here again locals telling the out of state elite riders asking about the Norton Nut. So please set me straighter on why i so poopped here yet have gun slinger show down reputation with just 3 seasons of exposure??? Very heady addicting high times I will never forget but want more so below is my current reasoning I would think other G force addicts might follow. Oh Yeah the other two OVER Cam bikes were a Laverda SFC 750 special one off extreme that was just nasty to here idle about to die between ear gut grinding blip up and almost spin outs trying to mover around off tarmac. Yet my P!! could eat all the above by 3rd gear yet hand off idle at 600 rpm lugging in 4th through tire deep sugar sand at 12 mph throwing the sand like boat wake but just a smooth roll on would instantly turn into a sand dune rooster tail throwing screamer to leap a bit over crest then settle back down to sight seeing speed in deep Fla. woods. This was the oldest school route so why is it not more common now a days?


Cams (2012)


I had to do a LOT of cogitating on Peel cam d/t the extremes she is intended for which realistically is fairly slow engine speeds on fairly high throttle, ie: just above lugging/chugging in and out of isolastion rpms on loose sloped surfaces which I get so scared of I routinely brake hard down to survive speeds for most blind crests and turns then instantly bore seeing way clear so nearly WOT back to curise or above, so after seeing some pretty hi strung vinteage cammed twin behaving like ordinary streer bikes in pits and yellow flag track operation, it made best since to get cam that was fairly whimmpy bit lumpy idle bangy idle d/t the early exht opening for normal sane mild throttle operation yet with just a bit of delay in taller gear it wakes up nicely to pull great or just a snick or two down for a struggle to hang on vs letting off for hook up. Ahhhhh, I had this twice so far on two Nortons so hope adding them together will blow me away.
Click to expand...

I am sorry Steve but the most interesting part of this post is that it contains a 162 word sentance.
 
Jerry Doe said:
Hi Jim,

You have convinced me. Now where do i get a 12a? I saw a website in Riverside California for webcams. Is it the same place http://Www.webcamshafts.com? They dont have much info on their site.

Cheers jerry
Click to expand...


Well, I am a webcam distributor. Since the early 80's.
I have them in stock.
Jim
 
Why cam a longstroke motor to tune best at an RPM range that is beyond its normally used rpm?
Click to expand...

Cycling is at your own risk as is following hobot. My professional advice is avoid both.
I am trying to comprehend the scope of Norton cams and why not shoot for highest performance hi rpm cam unless into parking lot stunts and over the ton is too rare to matter. I just do not think one is giving up much for somewhat delayed response down low if just gets better and BetteR fast as ya dare turn it. Would help if we had a data logger to give a sense of the power bands in real life. I know a bit of Chevy V8 and rpm limits so picked a all toque jet boat cam in mine with twisted wedge Alu Dart heads 10.5 CR to blpw past builder dyno owner sneering predictions on off the wall combo. Cam lift over 1/2 inch, int 290s, ext 300s. It was only good to 5600 but Oh La La - rather faster tha a good factory tune Combat, in 5000 lb cargo van. Anywho hope yours gives trouble hanging on.
 
Jim, I was looking at the graphs,- the horizontal axis doesn't show the timings you use in your motors ? Do you use the manufacturers' specs for timings and exhaust type, or do you adjust to suit the exhaust system you normally use ? Personally I always try to keep the power band peak, below the rev limit (7000 RPM). A non-restrictive two into one exhaust will normally knock the top of the power band and provide more torque.
 
acotrel said:
Jim, I was looking at the graphs,- the horizontal axis doesn't show the timings you use in your motors ? Do you use the manufacturers' specs for timings and exhaust type, or do you adjust to suit the exhaust system you normally use ? Personally I always try to keep the power band peak, below the rev limit (7000 RPM). A non-restrictive two into one exhaust will normally knock the top of the power band and provide more torque.
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All the cam graphs are made using equal lobe centers.
I adjust the cam timing to suit the exhaust system. Usually if I find the cam needs more than about 6 degrees adjustment from straight up -then I will adjust the exhaust. Jim
 
Not sure if this is the correct place to post, mods please move if appropriate.

I'm now the proud owner of the 2 cams in the photos:

Cams (2012)


Cams (2012)


They are both Norris cams, marked "380" and "480". As you can see, the 480(lower) appears to have an extra bearing surface. The cross drillings are connected to the drive (ie alternator) side of the cam .
Am I correct in my assumptions? The cases associated with them show no obvious mods for a bearing housing. Was such a thing ever marketed?
I'm aware of the flexi cam problem and that one or two people have have made their own versions of the centre bearing.

As an aside, a friend has given me scans of the Norris catalogue from 1979 (obviously including Norton stuff, but also Jap and European bikes.) Its 70 -odd MB but I'm happy to share if there's an easy way.
 
The Norris 480 is a full on drag cam. It is not suitable for street or roadrace. It must be used with BSA lifters ground to a 1 1/8 radius.

AFIK The machining in the center is just where the raised portion of that style cam was cleaned up with the grinder. It was not meant to be a bearing surface but it could work.

The 380 is a hot street grind. Jim
 
Thanks for clearing that up Jim!
This is for the drag bike I bought earlier this year. It has the BSA lifters, I'll have to check the radius. A quick glance shows the (480) contact patch to get dangerously close to the edge of the lifter, so may need some work there.

More questions to follow..... :)
 
snail said:
The cross drillings are connected to the drive (ie alternator) side of the cam .
Click to expand...

That's simply the old-style breather system as you find it on the Atlas and pre-72 Commando engines. There's two flats on the drive -side end of this kind of cam which drive the timed rotary disc. Compare the 1971 to the 1972 parts list and drawing. Therefore this is not a bearing surface - it's more like an incorporated centrifugal disc - and can't be used as one as long as that breather is still "active".


Tim
 
Thanks Tim,
This is making more sense now. This is my first Norton, so I'm a little in the dark over many aspects .

Cheers, Brian
 
SteveA said:
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! ...
Click to expand...

According to John Hudson, the standard Commando cam was the racing cam for the 650 SS "S - Sport", from a time when AMC owned Norton and also AJS, which used designations like CS, snd CSR. Thus, the standard cam for the Commando was the S (and the grind was from the twin-carb 650 and 750 predecessors); when the Combat cam was developed, it followed the designation system from all the way back to AMC -- just as Commandos for the first 4 years had an engine code prefix of 20M3, Model 20 - Atlas, Mk3. I made the mistake of telling him that I was planning to put a 3S cam in the 850 engine that we were building up for my Production Racer in the Experimental Shop at Marston Rd. -- I was afraid he was going to nail my toes to the floor and not let me leave until I told him that I was going to use a "S" cam -- which I did and never regretted it. Production racing in the 70s, a lot of people beat me by riding better (not that hard) but I never felt that anyone had motor on me everywhere from the slow corners to the fastest straights.

John opinion was mostly centered on the power characteristics of that cam, with the thought that good, smooth torque and power down low and midrange was of great benefit to all but the most skilled riders who could put that high speed power to work; and also for the factor of reliability and reducing strain of the valve train.

But that was 45 years ago. A computer designed cam that has optimized quietening ramps and opening profiles that are easy on the valve train and allow lower valve spring pressure might not make a single more horsepower than a 1970s cam but it will be a lot better cam, overall. (I like keeping my bike as it was when it rolled out of the factory gates but my next rebuild will be with a JS cam and lifters with the "beehive" springs with reduced spring pressures.)
 
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