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Cam followers : radius vs flat

Forums

hi, i've just aqquired a 650ss cam for my 99 dominator,hoping this will give a little extra grunt. my question is should i change the radius followers to the flat type which would have been fitted with this cam. also would someone please explain the difference between the two from a mechanical point of view? is it related to cam lift duration.

many thanks

pete

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Under no circumstances should you try and get more power from your 99. Remember that the con rods are over 50 years old and are not a particularly clever design. Alloy rods have unfortunate fatigue characteristics compared to steel ones. The 99 is the most fragile of the dominator series engines. I could post pictures of a collection of broken 99 con rods and destroyed barrels and crankcases...

My next and last 99 engine build is going together with a QR cam instead of an SS one and a pre 1960 cylinder head for the lower compression ratio. I would urge anyone who actually uses their 99 to do the same.

Gordon.

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Previously wrote:

Under no circumstances should you try and get more power from your 99. Remember that the con rods are over 50 years old and are not a particularly clever design. Alloy rods have unfortunate fatigue characteristics compared to steel ones. The 99 is the most fragile of the dominator series engines. I could post pictures of a collection of broken 99 con rods and destroyed barrels and crankcases...

My next and last 99 engine build is going together with a QR cam instead of an SS one and a pre 1960 cylinder head for the lower compression ratio. I would urge anyone who actually uses their 99 to do the same.

Gordon.

Well this has undoubtedly some truth and I have broken a few Dommie engines over the years but I'm not going to stop behaving like the teenager I was in the 60s. Where is the fun in that? Anyway one can always stick some steel rods in if worried.

Alan

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PS I lost the link for the Norton cam specs but I have just Googled it. I have added a couple of links that might be interesting although not wholly relevant.

Norton cam specs: http://www.oldbritts.com/11_30cam.html

Interesting thread: http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=65854&page=all

Peter Williams on cams: http://www.peterwilliamsracing.com/pw3cam.pdf

Cheers

Alan

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I'm with Gordon on this one. When we were 18 we were immortal, without a care in the world. Now I'm 65 and a pensioner I am just a touch more cautious with my life - I want to eke it out as long as possible! If you are rebuilding a 50 year-old piece of equipment that your life may depend on - DON'T OVERSTRESS IT! Old alloyrods can be home polished with your buffing wheel kit and should always be X-rayed if you want to take it to the limit. Engine seizures can equal death to the rider. You might not be quick enough in your old age to pull in the clutch before a disastrous seizure or break throws you off into the path of an HGV!Don't go for HC pistons and a 'hot' cam unless you're using new rods and bearings at least.

Back in 1965, at the first rebuild of my 99, I swappedits QR cam for a s/hSS one but kept the radiused followers (couldn't afford new ones!). I sold the QR to Barry Lawton - Sid's son, who was going to use it in his Domiracer (I think) on the I.o.M. I'm now looking for a QR cam or a new equivalent. Does anyone know of one? I haven't seen Dave Coates at shows or jumbles for years so missed my chance of one of his s/h cams.

My bike will be in relatively 'soft' tune with flat pistons (from Andover Norton of course) and probably new flat followers. I had the radiused ones reground to flat by Owslebury Crankshaft Services (I believe Norman White uses them) but one has a porous-looking surface so I might have to go for new.

Cheers, Lionel

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Having owned a collection of Norton99 bikes for the last 40 yearsandgiven most of them a realhard time I believe that I can add a little experience and knowledge to this Forum Thread.

Gordon is quite correct in that the 99 conrods are not the strongest but this is not too surprising if you consider they were originally designed for an engine producing less than 30bhp. A dozen yearslater and the same rods were then having to cope with a30% increase in power on the Nomad & 99SS models.

I never suffered from abroken conrod but knew several owners whodid. With hindsight, I now wonder if their actualfailures were caused by lack of oil to the big ends. In the earlier days ofthrashing the bikes,few people ever fitted the higher capacity pump ordouble speed drive. Plus most of us rode with cheap or old oil for lubrication and rarely checked the levels.

The worst problem I ever had with a rod was when a small end died.

I owned and rode two Dominator 99s that were converted to SS spec by fitting the 650 head, flat followersand camshaft. The first engine had an early dynamo barrel with the narrower pushrod tunnels. Consequently it had to use the standard and thinner 99 pushrods which whipped at high revs and caused valve float. When the fatter SS style of pushrods were tried they just just scubbed themseves to bits in the tunnels.

The second motor was built properly with eveyrthing above the crankshaft being 650 parts. This also had lightened rockers and camshaft followers. I used this engine for 30 years and it travelled over 90,000 miles. It was given new pistons and main bearings after about 60,000 miles. Nothing else was changed.

Unless you are going to continually be 'throttle' happy I see no problem with fitting an SS camshaft to a 99 engine. The QR camshaft was the forerunner of the SS item and I was informedthat it only really differs in having a little less lift at full opening.

Changing from radiused to flat followers does make a signficant difference to the breathing characteristics of the 88 & 99 engines and hugely improves bottom end grunt and mid-range pull.

So I would say to Peter fit the SS camshaft & some flat feet followers but don'tpush the engine above 6,500 rpm.

I would not recommend grinding down radiused followers to obtain flat faces. It makes them too thin in the centre and at max lift of the camshaftthey will tend to split.

Likewise, I have met many owners who had new Stellite pads fitted to their followers only to find them dropping off a little while later. Stick with originals.

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Previously wrote:

hi, i've just aqquired a 650ss cam for my 99 dominator,hoping this will give a little extra grunt. my question is should i change the radius followers to the flat type which would have been fitted with this cam. also would someone please explain the difference between the two from a mechanical point of view? is it related to cam lift duration.

many thanks

pete

Hello Pete You must change you cam followers to flat type .my 650 manxman was one of the first 650s built december 1960 and it as the ss cam and flat type followers , and years ago I had a 99SS it had the SS cam and Flat followers But the conrods had been made in aerospace alloy by my friend he worked at british Aerospace Brough East yorkshire that bike I thrashed the nuts off it ,I could not blow that engine ,I seen me ride to Cadwell Park and enter a race and finish in the top 10 riders and ride the bike 80 miles back home that bike had some 200 mile of hard thrashing and it just wanted some more ? what a machine it would keep up with my friends GS1000 on the M62 ,it did have a Quafe 5 speed gearbox , the motor kicked out 44 bhp on the rolling road it had twin Gardner flatslide carbs 28mm , i hope this helps

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Hi Phil,

The ground-off radius now give the followers an equal thickness of hardened material right across, rather than the thicker section in the middle when they were radiussed. Are you saying that SS flat based followers have a thicker hardened section - either all the way across or just at the centre? I ask this because I have never seen one.

Cheers, Lionel

Previously wrote:

Having owned a collection of Norton99 bikes for the last 40 yearsandgiven most of them a realhard time I believe that I can add a little experience and knowledge to this Forum Thread.

Gordon is quite correct in that the 99 conrods are not the strongest but this is not too surprising if you consider they were originally designed for an engine producing less than 30bhp. A dozen yearslater and the same rods were then having to cope with a30% increase in power on the Nomad & 99SS models.

I never suffered from abroken conrod but knew several owners whodid. With hindsight, I now wonder if their actualfailures were caused by lack of oil to the big ends. In the earlier days ofthrashing the bikes,few people ever fitted the higher capacity pump ordouble speed drive. Plus most of us rode with cheap or old oil for lubrication and rarely checked the levels.

The worst problem I ever had with a rod was when a small end died.

I owned and rode two Dominator 99s that were converted to SS spec by fitting the 650 head, flat followersand camshaft. The first engine had an early dynamo barrel with the narrower pushrod tunnels. Consequently it had to use the standard and thinner 99 pushrods which whipped at high revs and caused valve float. When the fatter SS style of pushrods were tried they just just scubbed themseves to bits in the tunnels.

The second motor was built properly with eveyrthing above the crankshaft being 650 parts. This also had lightened rockers and camshaft followers. I used this engine for 30 years and it travelled over 90,000 miles. It was given new pistons and main bearings after about 60,000 miles. Nothing else was changed.

Unless you are going to continually be 'throttle' happy I see no problem with fitting an SS camshaft to a 99 engine. The QR camshaft was the forerunner of the SS item and I was informedthat it only really differs in having a little less lift at full opening.

Changing from radiused to flat followers does make a signficant difference to the breathing characteristics of the 88 & 99 engines and hugely improves bottom end grunt and mid-range pull.

So I would say to Peter fit the SS camshaft & some flat feet followers but don'tpush the engine above 6,500 rpm.

I would not recommend grinding down radiused followers to obtain flat faces. It makes them too thin in the centre and at max lift of the camshaftthey will tend to split.

Likewise, I have met many owners who had new Stellite pads fitted to their followers only to find them dropping off a little while later. Stick with originals.

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Just a bit to add to Lionel's comments. You don't really need the high-capacity oil pump. Norton did a publicity stunt of running an 88 engine flat out for 24 hrs with just gravity feed to the crank - no oil pump. The centifrugral effect draws enough oil through to the big ends apparently. I have always used high-quality SAE 40 oil in summer, 20-50 in winter. The problem with 99 rods is that you don't know how far through their fatigue life they are. Is it 25% or 99%? No way to tell... What I dislike about 99 rod breakage is that it can destroy the engine whereas in an 88 the crankcases and barrels usually survive. I have raced my 99 (to a podium finish!) without engine problems. However, I have subsequently had rods break cruising at 70 mph on a long road trip. You just don't know when they are going to go. With a 650/750 you can easily obtain new rods, so no worries. I was advised by Les Emery that fitting carillo rods to a 99 can subsequently lead to crankcase cracking. I have no personal experience. My 99 now runs an Atlas engine with a rebuilt 99 engine sitting on the bench.

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Previously wrote:

I was advised by Les Emery that fitting carillo rods to a 99 can subsequently lead to crankcase cracking.

I have heard this but I do not know why Carrillo rods could lead to crankcase cracking. I have a couple of hypotheses but is anyone able to explain?

Cheers

Alan

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I have now seen pics of an SS flat-based cam followers and it's obvious to me that a ground off radiused one would be no thinner - in fact I think it's thicker but I can't get to mine at the back of the shed to measure yet! I'll check them and post the result when I do. So - if you can find someone who will grind them off properly (I use Owslebury Crankshaft Services in Winchester - thepeople Norman White recommended to me years ago) then you can do it without fear of the centres breaking, any more than any 50 year old SS follower would!

Re: the QR Daytona camshaft - it's quieter than standardand SS cams (the clue is in the name - "Quietening Ramps")and if it was good enough for Barry Lawton on his Domiracer, then it's good enough for anyone! There's no advantage in having a slightly higher lift SS on a road-going or touring bike anyway. Keep it soft-tuned! I will have a spare SS 'X1' cam for sale some time next year if I can find a QR! Swaps anyone?

As Phil says, rods break, particularly on the 99. Unless and until someone can tell me if they give an ample warning before they let go, I stand by my advice NOT to ever thrash them unless they've been X-rayed and crack-tested! It just ain't worth it! For those who say "Well, I thrashed mine without any trouble" I say - that applies to just about anything mechanical or electrical so is a pointless statement! Things often ARE fine until they break or explode! Not much consolation in that eh?

In my days as a mechanic I specialised in Jaguar XK engines (carburettor models). I once picked up a brokenXJ6 on the M3 which had thrown a rod through the side of the cast-steel crankcase! PHEW!! It was actually because they had used the same big-end bolts and nuts after a regrind and rebuild - not because a rod have broken, but it's another warning about not using certainold parts. My Bro' had a Triumph 2.5 PI in the 70s and I once had to rescue him after his prop-shaft fell off! He'd recently had a new Balljoint fiitted by a garage (Not me!) and they'd re-used the same bolts andNyloc nuts! SCARY! Nylocs are "use-once" nuts! When I went to undo the other end of the shaft the spanner just fell round under its own weight as the nuts had slackened right off - this was the front end which luckily didn't come off when he was driving! That can dig into the road and remove the rear suspension as well as part of the floor!

I only mention these events as a warning for rebuilds!

"Let's be a bit carfeful out there!"

Cheers, Lionel

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Hi Gordon - yes I'm interested and have written to your email address. Just waiting for your reply.

Cheers, Lionel

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Hi again Lionel - nothing in my inbox - could you try contacting me through my website please? www.scothebs.co.uk Gordon.

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Thanks Gordon, I used your hyperlink above so I couldn't have made a mistake with the address. Have mailed you via your very interesting website! Lovely sheep!

Cheers, Lionel

I have to agree with Permalink. I having ridden 88s and 99s  on the road in the 60s and raced them for four years 88s & 99s up to 1970 the only way I have ever ridden them is by thrashing the poor things to with in I rpm of their life and I still do at 73!! the only blow up I have ever had  was with one  lap left  of the Manx GP in 1968 and that was a broken exhaust valve and I still road the domie at full throttle back to the pits on one cylinder down the mountain, ok so that was not a very bright idea!! but we never gave up won't go into detail about what that 8 or so miles did to the inside of that poor engine with a valve head bouncing around at 5000+ rpm it found its way into the sump and continued to bounce around there for some time. My 88 café racer that I ride  now   ( NOC calendar Oct 2016)  is soft tuned with a 650ss head, twin carbs 650ss cam with flat foot followers I would have fitted 10.2 to 1 pistons if I could have found them, with standard original bottom end. That bike is now quite well known for the last six years I have ridden it  in the PR5 parades with the NOC at CRMC race meetings all over the country and in the VMCC festival of a 1000 bikes. and still ridden with in 1 rpm of its life I will say I am now showing  my age and the 88s in the meeting at Snetterton last year with a strong tail wind down the back straight I saw the rev counter moving towards 7000 my hand moved onto the clutch leaver!! I would rather use old Norton parts than buy new remanufactured ones if and when I ever have one fail I might think again but like the valve that broke I look to what I did to the inside of that engine IT WAS NOT SOFT TUNED. With those few mild changes head, ss cam, flat foot followers I would be confident of many miles of plodding around on the road which most old road riders do and that is me too on the road I pull out my featherbed M50  who needs more than that on the roads of the UK today?? The real fun is with the NOC at CRMC meetings join us its free and we need more riders to support the event check the Roadholder for details.

 

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If you decide to fit new shells to the big ends ,be sure that they are free to turn. Old rods can go oval and new shells can lock the motor up , rods then can snap.Also take care to fit rods exactly as found, Load reversal not good policy.

Thanks Jan.  I used to go to Kempton about 3 times a year but haven't been for a while.  I never saw Dave there, only at Shepton or Stafford.  Perhaps he only goes in December - I never do.  I don't need a camshaft now as I bought a QR one.  I still have the "X1"  SS cam to sell, as well as all sorts of bits going back to a 1955 "88" but too many home projects going on to tidy my shed & workshop to be able to find things!

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HI Jan/Lionel,

   I spoke to Dave at Kempton yesterday and it was business as usual. He has had a few family issues but said he would be at Shepton Mallet next month.

Hi Gordon, you say that you recall Norton running an engine for 24 hours without an oil pump, just gravity feed. Any idea how they evacuated the oil from the crankcase? Left the sump plug out maybe !!

In reply to Pete, by all means go ahead and fit  the SS cam but don't expect anything earth shattering to happen.

Many people go down this road but it takes more than a change of camshaft to make even a small ammount of difference to power output.

I would be suprised if you actually notice a benefit from doing nothing more than fitting the cam, it certainly shouldn't cause any risk to your rods.

With regard to the rods, I ran 99s for many years and later a 650SS, eventually fitting a chair , I wasn't  known for hanging around and they were all, over time driven hard. I never had broken rods or blown up engines and I always got to wherever I was going. I can say quite honestly that my Norton's never ever let me down.

Thanks Richard.  Perhaps he's been at Kempton when I've visited but I somehow didn't spot him. I tend not to go to Shepton much as it has been disappointing in recent years with much fewer stands. 

The old ones are forged so have a better chance of longevity.  The machined-from-billet-types don't sound so good as the grain won't follow the line of best strength - the whole point of forgings.  However, when using 50 or 60 year-old rods you should polish them to within an inch of their lives so that they look like chrome, then get them x-rayed - or maybe the other way round if you intend to thrash the bike.  Try to get them to weigh the same within a few grams if poss - complete with their caps and bolts of course. Nicks and scratches can propagate cracking under high stress.

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Recommended bed-time reading is Peter Williams' account of delveloping his range of PW Camshafts. By the time he had got to number 7, he was offering a camshaft that was not pushing the valves up much higher but was opening a little sooner and staying open by the same amount for longer. The result being more torque and consequently BHP across a greater rev range.

This echoes in a way the development of the Norton Twin camshaft from the Model 7 onwards. The Model 7 camshaft basically opens then shuts straightaway limiting the power output. Which actually wasn't bizarrely a bad thing as too much power cooked the head and led to all kinds of problems with sticking valves and fuel vaporising issues..

This camshaft was followed by the Daytona version with fatter sides and then the QR version with both fatter sides and a little more lift. The former fitted in 1956 and the QR from 1958 (roughly) on.. The next camshaft was the SS which arrived from 1960 onwards. This was not too much different from the QR profile but proved that a few more thou of lift and duration gave even more oomph,  especially on the 650 engine. The Norton race boys had already found out that fitting flat-footed followers in their Nomads along with QR camshafts, HC Pistons and twin carbs gave  buckets more BHP and so these became a standard feature from 1960 on all the models designed for speed.

You can fit the flat-foot followers into any of the early engines without changing the camshafts and get a 2 to 3 BHP  boost in low down power. That's nearly 10% on a model 7. The attachment shows all 4 pre-1962 Dominator camshafts along with a very early Dunstall part-exchange 'go faster' item from around 1959. Let's play 'spot the goodie'!!!

Attachments
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Peter:

Can you state left to right what we are looking at?

Mik

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I can not remember which is what  Mike. The photo was taken too long ago.  I would guess that the one with no number is the Dunstall and that with the pointy cam profile is probably out of a Model 7. Perhaps one of our wiser Dominator Engine contributors can ID them? Where's Anna when you need her?

 

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