99SS valve spring lengths

Those are some crazy springs you have in that bike, I think you should toss them in the trash. Stock springs were 1.7" for the outer and 1.531" for the inner. So there is a chance you have the wrong springs for your engine, or maybe some racing springs someone added to it at some point. I like Dunstall's advice for stock springs, he says if they have collapsed more than .187" then they should be discarded and new springs fit. Of course there is a recommended installed height for the springs, and also recommendations on keeping them a certain dimension from coil bind at full cam lift. If your valve seats have been ground and sunk a bit then you may have some shimming etc. to do to get everything back to spec and your valve geometry right.

The factory parts book lists the same spring for the 88ss, 99ss and 650ss, so if you need new springs buying a set of new factory springs for the 750 or 850 Commando would be the current correct replacement part for the bike. Norman White told me he likes to use these new factory springs with the PW3 Cam on street bikes including Dominators, so they should certainly be good for the factory SS cam. I would be interested in corresponding with you and looking at some photos of your 99ss. I have three 62' SS bikes and some spares for them so maybe we can help each other out swapping information etc..

I don't have the figures for valve spring length to hand, but the standard head valve springs are longer than the downdraught head valve springs. Do you have a downdraught cylinder head? I may be wrong here, but some 99SS models may have the standard head but a twin carb manifold. I am sure I will be corrected on this... Gordon.

Previously wrote:

I don't have the figures for valve spring length to hand, but the standard head valve springs are longer than the downdraught head valve springs. Do you have a downdraught cylinder head? I may be wrong here, but some 99SS models may have the standard head but a twin carb manifold. I am sure I will be corrected on this... Gordon.

Different length springs for DD and non DD heads is correct.

The 2.01 & 1.7" springs you have are the earlier ones. Does your 99SS have the interim head, pre downdraught but with the bigger inlet valves and the milled crosses between the rocker shafts? The Norton parts lists are (surprise) rather ambiguous. The 61 - 62 list specifies one set of springs for the 88, 99 Std & DL, and a different set for 650 Std & DL. The 63 - 65 list specifies the same springs for all models 88SS, 650SS, 650/99 & Atlas. I can't remember what I put in my 99. I will look through my files later.

The 1961-1962 parts book, publication PS 214, does list one type of springs for the standard 88 and 99 models, and it lists another part number for the 88ss, 99ss and all 650s. Not ambiguous at all......

SS Nortons did not come on the market until well into 1961, and never used the old style heads that were smooth between the rocker boxes. But that does not mean after 50 years that someone has not retrofitted parts from many different bikes, which is one reason I still would like to see photographs of the bike and it's engine etc.....

Benjamin previously wrote:

The 1961-1962 parts book, publication PS 214, does list one type of springs for the standard 88 and 99 models, and it lists another part number for the 88ss, 99ss and all 650s. Not ambiguous at all......

SS Nortons did not come on the market until well into 1961, and never used the old style heads that were smooth between the rocker boxes. But that does not mean after 50 years that someone has not retrofitted parts from many different bikes, which is one reason I still would like to see photographs of the bike and it's engine etc.....

I agree, the 1961 -62 parts book on its own contains no ambiguity. That is not what I wrote.

Neither did I write that SS Nortons used old style heads. However, few, if any, 99SS bikes had the downdraught head.

I agree that some photos would be helpful.

I hope that this is unambiguous.

Alan

If you have either the QR or SS camshaft in your engine then go for the later, shorter and fatterSS springs. Otherwise, you will get valve float at high revs.

The other thing to watch out for is the pushrods in your engine. They ought to be the fatter SS type to cope with the heftier SS springs and SS camshaft. The earlier thin versions may bend if combined with the previous SS gear mentioned.

Finally, just to add to the muddle. If you do have the fatter SS pushrods then you also really need a proper 99SS or 650SS barrel with the slightly enlarged pushrod tunnels to go with the fatter SS pushrods. If your barrels are not the originals then check this out before rebuilding the motor. Earlier pre 1960 barrels do not like SS pushrods inside them due toa clearance problem.

Steve

Your motor is similar to the one I'm running at the moment although mine started out in a DL. I checked the springs and I used 067822/3, the later, shorter, fatter ones as Phil describes them.

Cheers

Alan

Your head is as I suspected - the pre-downdraught one. I have used that type with an SS camshaft and the early (pre downdraught) longer springs very successfully. I am a bit wary of using the shorter, high rate springs. No point on putting unnecessary load on the valve train. I would rather have valve float than break a con rod at high revs... Gordon.

Previously wrote:

Previously wrote:

Those are some crazy springs you have in that bike, I think you should toss them in the trash. Stock springs were 1.7" for the outer and 1.531" for the inner. So there is a chance you have the wrong springs for your engine, or maybe some racing springs someone added to it at some point. I like Dunstall's advice for stock springs, he says if they have collapsed more than .187" then they should be discarded and new springs fit. Of course there is a recommended installed height for the springs, and also recommendations on keeping them a certain dimension from coil bind at full cam lift. If your valve seats have been ground and sunk a bit then you may have some shimming etc. to do to get everything back to spec and your valve geometry right.

The factory parts book lists the same spring for the 88ss, 99ss and 650ss, so if you need new springs buying a set of new factory springs for the 750 or 850 Commando would be the current correct replacement part for the bike. Norman White told me he likes to use these new factory springs with the PW3 Cam on street bikes including Dominators, so they should certainly be good for the factory SS cam. I would be interested in corresponding with you and looking at some photos of your 99ss. I have three 62' SS bikes and some spares for them so maybe we can help each other out swapping information etc..

Hi Benjamin

Thanks for the response on the springs. It seems that they are near right for 1961.

I don't think my 99SS would be any good as a reference as it has a commando engine with twin coils, goldie exhausts, twin concentrics etc.

Do your 99s have the small bore siamese pipes, and are they 2 or 3 piece? I can't figure out how you would get the rings over the junction if they were 2 piece. I am planning to turn it back to 99SS spec but with a belt drive and 12V.

Steve

You might not have understood some of the things added above, but your bike did not originally come with those long springs, so you are not trusting Norton's judgement at all, you are going against it.

It seems like someone may have done some poor parts swapping in the past on your bike, maybe that is why it has been sitting in pieces for so long, and it sounds like you are trying to repeat history.

If your bike is in fact a real 99ss, then it is a very rare bird, especially if it has it's original crankcase and frame. It would be a real shame if because of a poor effort on the engine rebuild it ended up blowing badly and wrecking a rare piece of Norton history.

If I dig around, I probably could come up with a good set of used SS style springs that I would gladly give you if you pay the postage.

I'm just going on shaky memory here, but the 99 SS with the pre-downdraught head had the long valve springs, not the short high-poundage ones. So fitting later short springs would be wrong. As for wrecking the engine, I have used the long valve springs on a 99 with both pre and post downdraught heads for many tens of thousands of miles with no problems. I think Steve actually has a clear understanding of the above discussion.

"Shaky memory" is not necessary, as the 1961-1962 parts book, the one printed when the 99ss was actually in production, very plainly shows one type of valve spring for the 88ss, 99ss and 650ss, and another for the standard and Deluxe 88 and 99.

The SS Nortons that left the Bracebridge Street works in 1961 and 1962 were plainly stamped "88ss", "99ss", or "650ss" on the crankcase back by the breather, if the mark is not there then it is either not an SS, the crankcases have been blown and replaced, or it is one of the 99 standard or Deluxe bikes that left the factory with some of the performance parts which are again, all listed in the factory parts book for that year.

Since the 99ss was only sold from part way through 1961 until the Bracebridge Street works was closed at the end of 1962, and did not make the move to the AMC works, yes it is one of the rarest Norton motorcycles produced. Start looking for one for sale, you will not find any, but OHC Internationals and Manx bikes and projects do pop up regularly....

Previously wrote:

I am rebuilding a 99SS engine out-of-a-box which hasn't run since 1977. The outer springs are 2.01" long and the inners are 1.7" - does anybody know if they need replacing? My Haynes manual is at the grinders, but I can't recall if they give figures for a minimum length

Steve

These springs are correct, and at correct length, so do not need replacing, as the 99ss did not use an SS cam or head, being merely a 99 with a twin-carb manifold bolted on. I am amazed at the ignorant opinion posing as fact on this site. Dale Middlehurst

Hello well the valves and valve springs are all from the Norton Manxman 650 And also the crankcases too and push-rods camshaft and cam followers All found there way on to the (99ss) and (88ss) But for some reason Not the Cylinder Head As the Manxman Had The first Downdraft twin carburettor Cylinder Head design ,with inlet sleeves fitted in-between the cylinder head and inlet spacers,now hard too find,

Yours As ever Anna J Dixon

Dale previously wrote:

These springs are correct, and at correct length, so do not need replacing, as the 99ss did not use an SS cam or head, being merely a 99 with a twin-carb manifold bolted on. I am amazed at the ignorant opinion posing as fact on this site.

The 99SS was not merely a 99 with a twin-carb manifold bolted on.

I have been thinking back. I had my first 99 in 1969. It was a slimline but had the earlier alloy head, not the one with the crosses between the rocker shafts, and an after-market twin carb manifold made by Myers. I remember discussing rebuilding the engine with Bert Saunders. Bert had a Norton shop near Southend on Sea and ran a small race team. He managed to get his Atlas, piloted by Billie Nelson, to 2nd place in the 1968 Production TT behind Ray Pickrell on the Commando. Although I no longer have my notes from back then, I am fairly confident that Bert recommended using the later valve springs. That motor had the QR cam in it.

Thinking about all the variables that can affect the valve gear geometry and function, I suggest that irrespective of what might have been in the motor when built, the only approach to take when rebuilding today is to consider from an engineering perspective whether the parts being used work satisfactorily together.

Cheers

Alan

As I don't trust my memory, I have just spent an hour in the garage comparing measurements from a 99 head similar to the one Steve is using, and a 650SS head. There are no differences in the combusion chamber recess dimensions. There are no differences in the distances from valve seats to tops of valve guides. The major differences are, of course, the port shapes. There are slight differences to the finning. I can see no reason dimensionally why later springs should not be used in Steve's head. It also seems to me that as the later springs are variable rate, there is not necessarily a greater max load on the valve gear.

Cheers

Alan

Rare head for a rare bike. That late style non-downdraught head is discussed in the Norton maintenance and owner's manual publication p106. It gives the same compression as the later 650 style head, the 1959 and earlier heads gave one less point in compression.

Early downdraught 650 heads had some of the same casting numbers as these heads, like they just swapped a few cores but not all of them to make them at the foundry. The parts book lists the same valves to be used in all twins for 1961.

The Standard and Deluxe 88 and 99 never got the SS cam, springs or pushrods in 1961 or 62' though. So besides being marked as a "99SS" from the factory, the other differences between the 99ss and the standard Model 99 would be the addition of twin carbs and the SS cam and valve gear.

The twin carbs and some high compression pistons and a lot of other options are listed for the standard Dominators and bikes equipped that way show up, but the SS cam is not found in the option list. This does not mean that a special friend of the Norton works could not get anything they wanted though. Sometimes added options were listed in the factory records, definitely worth a look into.

Apparently all Model 99 roadsters had the same compression ratio, even the 99SS, as no special pistons are listed for it as regular replacements, someone wanting higher compression would have to order it optional.

Over here in the USA you never see slimline model 99 Nortons very often. Since we started getting the 650 at the beginning of 1961, and the 750 Atlas in 1962, there was not a lot of reason for USA riders to pick a Model 99 or 88 off the showroom floor and if you do see a small Dominator over here chances are it was imported personally by a serviceman etc..

Yes, first find out what the bike actually is. It could be a 99ss, a Standard, or even a DeLuxe that someone has taken the bodywork off of, anything could be possible after 50 years. Dave Catton, the heavy twins records officer, has a really nice slimline standard he restored to look like new and he is very prompt with records requests.

The only difference in the valve train parts between the 99ss and Standard were the springs, the two bikes took the same CYLINDER head, valves, "top cups" and other parts so the two types of springs would be mechanically interchangeable between the two bikes for sure.

The Norton SS Dominators were all specified with twin carbs, they were supposed to be "sports-specials" for fast touring or production racing. Having the standard 99 springs and a single intake are something that of course, a 99 Standard would come with. I would doubt that the standard Dominator valve springs have been made for a long time and no matter what cam is in your bike, it would be very easy to find a good used set of the later springs as they were in production until the last Commando came off the line in the 1970s.

Intriguing... I am NOT going to take the standard long springs out of my 99. It's perfectly happy with the type it had from new. Gordon.

In Gordon's case, if his 99 has a pre-SS cam, the pre-SS springs are what it came with and should work fine as long as they are not worn out.

The 1961 88ss and 99ss had the non-downdraught head(not the 650 style head) and twin carbs. For 1962 the 88ss got the 650 head, the 99ss was not specified with it, but almost no model 99 Nortons were built in 1962 anyway so almost no one has to worry about it.

Bracebridge Street stuck carbs on the 650cc bikes that were smaller than the ports in the new downdraught cylinder head, so they pressed steel sleeves into the inlet ports to bring them down to the size of the carbs! The 650 ran good with those carbs and sleeves, they had lots of mid-range. The 88ss got the same sleeves as the 650 when it switched to the 650 head.

If your engine is apart, then you should be able to look at the camshaft. The 1961 99SS cam would have a "X1" stamped on it somewhere, and the Model 99 Standard cam would probably have "QR" stamped on it. If you have the QR cam and you are going to use it, then the old-style springs would work fine with it. The X1 cam though is a hotter job and Norton put the new style springs in with it so young men would have a tougher time blowing the engine up.

Your crankshaft should be one of the good ones with the small 5/8" diameter sludge trap in it instead of the 1" diameter sludge trap the pre-1960 99 had. Your pistons should have a slight dome on the top, I have heard of guys having trouble finding 99 pistons and sticking flat-top 650 pistons in, then you end up with low compression and low power.

The 88ss at 500cc fit into a lot of racing classes, so it makes sense that Norton would stick the 650 head onto it at some point to make it legal in production racing. It also makes sense that Norton would drop the 600cc Model 99 when they had 650cc and 750cc bikes on the assembly lines.

Please keep us up to date on your Model 99 project as you uncover information on it and get some photographs taken of it!

In Gordon's case, if his 99 has a pre-SS cam, the pre-SS springs are what it came with and should work fine as long as they are not worn out.

The 1961 88ss and 99ss had the non-downdraught head(not the 650 style head) and twin carbs. For 1962 the 88ss got the 650 head, the 99ss was not specified with it, but almost no model 99 Nortons were built in 1962 anyway so almost no one has to worry about it.

Bracebridge Street stuck carbs on the 650cc bikes that were smaller than the ports in the new downdraught cylinder head, so they pressed steel sleeves into the inlet ports to bring them down to the size of the carbs! The 650 ran good with those carbs and sleeves, they had lots of mid-range. The 88ss got the same sleeves as the 650 when it switched to the 650 head.

If your engine is apart, then you should be able to look at the camshaft. The 1961 99SS cam would have a "X1" stamped on it somewhere, and the Model 99 Standard cam would probably have "QR" stamped on it. If you have the QR cam and you are going to use it, then the old-style springs would work fine with it. The X1 cam though is a hotter job and Norton put the new style springs in with it so young men would have a tougher time blowing the engine up.

Your crankshaft should be one of the good ones with the small 5/8" diameter sludge trap in it instead of the 1" diameter sludge trap the pre-1960 99 had. Your pistons should have a slight dome on the top, I have heard of guys having trouble finding 99 pistons and sticking flat-top 650 pistons in, then you end up with low compression and low power.

The 88ss at 500cc fit into a lot of racing classes, so it makes sense that Norton would stick the 650 head onto it at some point to make it legal in production racing. It also makes sense that Norton would drop the 600cc Model 99 when they had 650cc and 750cc bikes on the assembly lines.

Please keep us up to date on your Model 99 project as you uncover information on it and get some photographs taken of it!

My 99 for the last 20 years or so has been running an SS cam, a downdraught head and long springs. Dearie me, I expect stern men in black to turn up unannounced and drag me off to an unspecified country for exquisite torture...

P.S. I have in the past raced to a podium finish on standard valve springs.

Gordon previously wrote:

My 99 for the last 20 years or so has been running an SS cam, a downdraught head and long springs. Dearie me, I expect stern men in black to turn up unannounced and drag me off to an unspecified country for exquisite torture...

P.S. I have in the past raced to a podium finish on standard valve springs.

Guess what springs the 650SS head I have was fitted with!

Mr. Johnston and Mr. Dawes are telling us that over the years that backyard mechanics and private individuals have tried things the factory did not do, which is unprecedented and revolutionary news, thanks. Used valve springs are certainly okay to use. Dunstall suggested that if the free length of the late Norton springs has sagged more than .187" then new ones should be fitted. That is a bit more than 10% sag, so maybe a similar rule could be calculated for re-using the early springs. Mr. Dunstall also packed his springs to within about .045" coil-bind, something that a careful mechanic can do that the factory probably did not watch as closely on the assembly line. At one time the 48th 650cc Norton built, an all original bike, overheated due to riding with a loose carb in freezing weather. One exhaust valve warped, the plug sidewire melted off and porcelain came loose in the body, both valve springs were ruined by the heat sagging badly. This bike had the late-style 1.7" springs. I went through a box of used springs and using Dunstall's rule pulled out the best of the lot, those closest to factory spec, and put them in the bike shimmed up along with some nice used valves and a light re-grind of the seats and valve faces. The bike ran better than it had before and happily revved to over 6K, which is around where I like to stop on street bikes I wish to last. Currently I am assembling a 62' 650ss, that is a very original bike on standard bore still. The engine has been cleaned and I am reassembling it with some later used but very low-mileage Commando rods, valve springs, main bearings and maybe a few other parts that should have many years of service left in them and even increase the reliability over the factory parts. I will put the original rods etc. in a box in as I think the history is important, and it might be to some future owner also. Used and non-spec parts are important options that knowledgeable and careful mechanics can get good results with and save money with also. Alongside that option though, it is nice to have the history of Bracebridge Street and the parts and facts they recommended to give the builder or restorer all the perspective they might want.....

Mr. Johnston and Mr. Dawes are telling us that over the years that backyard mechanics and private individuals have tried things the factory did not do, which is unprecedented and revolutionary news, thanks. Used valve springs are certainly okay to use. Dunstall suggested that if the free length of the late Norton springs has sagged more than .187" then new ones should be fitted. That is a bit more than 10% sag, so maybe a similar rule could be calculated for re-using the early springs. Mr. Dunstall also packed his springs to within about .045" coil-bind, something that a careful mechanic can do that the factory probably did not watch as closely on the assembly line. At one time the 48th 650cc Norton built, an all original bike, overheated due to riding with a loose carb in freezing weather. One exhaust valve warped, the plug sidewire melted off and porcelain came loose in the body, both valve springs were ruined by the heat sagging badly. This bike had the late-style 1.7" springs. I went through a box of used springs and using Dunstall's rule pulled out the best of the lot, those closest to factory spec, and put them in the bike shimmed up along with some nice used valves and a light re-grind of the seats and valve faces. The bike ran better than it had before and happily revved to over 6K, which is around where I like to stop on street bikes I wish to last. Currently I am assembling a 62' 650ss, that is a very original bike on standard bore still. The engine has been cleaned and I am reassembling it with some later used but very low-mileage Commando rods, valve springs, main bearings and maybe a few other parts that should have many years of service left in them and even increase the reliability over the factory parts. I will put the original rods etc. in a box in as I think the history is important, and it might be to some future owner also. Used and non-spec parts are important options that knowledgeable and careful mechanics can get good results with and save money with also. Alongside that option though, it is nice to have the history of Bracebridge Street and the parts and facts they recommended to give the builder or restorer all the perspective they might want.....

Delighted to have added to Mr Gradler's extensive stock of knowledge.

Previously wrote:

Alan

I agree in principle about using later, proven technology where available, but the missing parts of the puzzle are the valve stem length above the lower collar and the size of the step in the upper collar.

The way I see it, ignoring subtleties such as harmonic resonances in the springs, the only two parameters are the force required to compress the springs to their fitted lengths and the compression force they each exert (inner & outer) when the valve is fully open. And not being coil-bound of course.

As the cams are interchangeable across all SS's, and Anna J Dixon has confirmed that other parts of the valve train are common between downdraught and non-downdraught SS's (presumably including the rocker arm ratio) the springs should work just the same way in the99SS as in the 650SS - if their fitted lengths are the same. The compressed length will not be a variable, given the commonality of all other factors. BTW my 99 definitely has flat cam followers.

Does anybody have the data on the fitted lengths in a 650SS, Manxman etc handy?

Best

Steve

Hello Steve I have all the parts numbers for The Norton Manxman 650 valve spring free length outer 1:700" inner 1:531" and its the same for the Atlas too ,hope this helps

yours anna j dixon

Anna, Steve doesn't have a Manxman, he has a 99. The original question Steve asked was were his valve springs correct for his cylinder head. The answer is yes (pre-downdraught head, long springs). There have been considerable efforts to convince him to fit the later, short springs as fitted to downdraught heads. The choice is entirely his.

Incidentally, I am sure my Engineering lecturers and tutors would have agreed with Mr Gradler's description of me as a backyard mechanic.

I agree with Gordon.

A "Tuning Norton" article by John Hudson in Motor Cycling Feb 12 1966 included the following comment on valve springs:-

"It is the downdraught head which uses short valve springs and SS owners with the earlier heads should use the standard springs.

Theshort springs can bepacked up to suit SS models with the pre downdraught head but trouble is usually experienced with maintaining location of the assembly."

John Hudson did know a thing or two about Nortons.

Iain

Benjamin is undeniably correct when he writes, "backyard mechanics and private individuals have tried things the factory did not do". Although I think I can safely assert that today we have no complete knowledge of what the factory did.

Iain's post is interesting but it makes no sense to me. The later springs should be as secure in the earlier SS head as in the downdraught head. By earlier SS head I refer to the one fitted to Steve's bike (and mine). The dimensions that matter are the same. I am going to try some springs of both types in a spare pre-downdraught head later. (I have to put up a new curtain track before I can listen to some jazz and potter about in the garage.)

Were the alloy heads without the cross marks ever used on early SS bikes? I don't have one of those heads to measure; were the dimensions different? If I ever knew, I've forgotten.

Another thought; given the way sub-editors hack copy about, I wonder if Mr Hudson's remarks had become over simplified.

Cheers

Alan

I talked with John Gregory about this before, the man who built the Hogslayer Norton drag-bike for T.C. Christenson to ride. He also had a very fast Model 88 roadracer in the 1960s. He said that he turned the later domed Model 99 pistons down to a model 88 oversize to make light high compression pistons for his race bike.

Also I have a .040 over 88 cylinder here I would like to use someday. Standard Model 99 pistons would be right about .080 oversize for a Model 88. On my cylinder I measured the cylinder wall thickness at the front where the fins are shaped to allow the nut to go up onto the front cylinder head studs and I found that they are currently .108" thick there, which means that bored to .080 I might have as little as .068" of wall left at that point. I am sure that it would be easy to find recommendations for cylinder wall thickness and see how it compares.

For touring I would think you could get away with a lot of things like this. For some reason back in the day Norton only offered up to .040 over in the parts books, and I know the racing boys like to find them as thick as they can get them.

I have thought about asking a good piston engineering company if they would take a few sets of old 99 pistons I have and turn and profile them to a 88 oversize, it is on my list.

Every time I go to post on this forum it says I have not typed anything and to re-type it, then when I do that it either posts it twice, and now it has posted something to this thread which I wrote for another one. Has to be the worst forum software ever written.....

Twin carbs were an option on both of the Heavy twins from May 1958 onwards. Tests with these on the Nomad off-road bikes had shown a substantial power boost when used in conjunction with high compression pistions, flat foot cam followers, Daytona and later QR camshaft. All of the above were available as options to purchasers of new machines.

The 1961 88SS & 99SS engines both came with the 650 sporty bits. Shorter valve springs, SS camshafts and fatter pushrods. The cylinder heads for both of the initial models were standard heads with compression ratios of 8.5 to 1 (88SS)and 8.25 to 1 (99SS). An option of 9.0 to 1 pistons was also offered/recommended as an option for the 99SS engine. very few 88SS machines were built before a change to the SS head whereas the 99SS soldiered on using a standard head that was polished and ported.

Records/photos show that the 99SS was constructed using the 650 type of crankcase with the bulged section to accomodate the 650 crankshaft stroke.................but were similar cases used on the 88SS???

I ran a 99SS for nearly 30 years using bothan original head and a 650SS version. The 650 head was used 'go-faster' times and the original head for touring. The latter head being converted to single carb and also mistakenly reconditioned with early pre-1961 2" valve springs. These springs were not a problem until the engine was asked to rev up to 7000rpm at which point I always got valve float. Some time later when decoking this headI noticed that bothpistons and respectivevalves had serious damagewhere they had been making contact.

A lesson learned the hard way!!!

It will be interesting to see what information Mr. Marshall digs up on his bike for us when he gets his cases back, a factory records check and sees what type of camshaft he has for the bike.

I have a couple of 1962 88ss bikes that have the 650 style cases, but have never seen a 1961 Model 88 first-hand that I could inspect for this feature.

The first batch of 650 Nortons had serial numbers in the 936xx range. I would not be surprised if some 88 and 99 bikes had old-style cases for a while after the 650 Manxman was being built until stocks were used up.

Someday hopefully we will get reports from enough owners of Dominators with numbers in the right range to clear up that mystery.

Previously wrote:

It will be interesting to see what information Mr. Marshall digs up on his bike for us when he gets his cases back, a factory records check and sees what type of camshaft he has for the bike.

I have a couple of 1962 88ss bikes that have the 650 style cases, but have never seen a 1961 Model 88 first-hand that I could inspect for this feature.

The first batch of 650 Nortons had serial numbers in the 936xx range. I would not be surprised if some 88 and 99 bikes had old-style cases for a while after the 650 Manxman was being built until stocks were used up.

Someday hopefully we will get reports from enough owners of Dominators with numbers in the right range to clear up that mystery.

Hello Ben well we all seen to called the high lift cam that was Fitted in to the 650 Manxman first the SS cam for some reason . its the development of the Daytona camshaft really . And I can also confirm That The (88SS) &(99SS) & (650 Manxman) & Atlas Had all the same valve springs . being 1:7 outer springs &1:5 inner Springs . And I had a (99ss) For some time in Cafe racer mode, And it had 10.5.1 High Compression piston's made for racing and specially made connecting rods and big end shells and Gardner flat side Carburettors on it too ,And a 5 speed gear box, a racing magneto fitted it had a special light slimline frame SIF bronze welded and alloy tank and oil tank alloy wheel rims and rear sets it was in Metallic blue . and it would keep up with a GS 1000 and I could thrash it all day and it would just come back for some more . I use to ride to a race meeting and enter it for the last race and finished in the top 10 . then ride it all the way home . not sparring the horses . And I wish I had that bike now. my dad sold it when I was at sea . yours Anna J Dixon

Steve Marshall: "so I am wondering if there ever was a factory twin carb, non-downdraught option for any SS Dominator" Why would you wonder that? The parts list lists one manifold for the 61' 88ss and all 99ss because that is all that was needed to mount two carburettors. It was a dual carb intake machined from one block of aluminum that bolted and bridged across the back of both intake ports. Norton started using this type of intake in the early 50's on the Daytona-style Dominator racing bikes, then used it as an option available on the 58' and later Dominators, and finally as standard fitment to the 88ss and 99ss. Over that period of about nine years they did modify it here and there a bit to fit different carbs and the larger stud spacing on later heads. A friend of mine with two of the 50's Daytona bikes says the early ones like his were actually machined from billet, but a later one which I sold a bit back looked to be machined from a casting.

Steve Marshall: "so I am wondering if there ever was a factory twin carb, non-downdraught option for any SS Dominator" Why would you wonder that? The parts list lists one manifold for the 61' 88ss and all 99ss because that is all that was needed to mount two carburettors. It was a dual carb intake machined from one block of aluminum that bolted and bridged across the back of both intake ports. Norton started using this type of intake in the early 50's on the Daytona-style Dominator racing bikes, then used it as an option available on the 58' and later Dominators, and finally as standard fitment to the 88ss and 99ss. Over that period of about nine years they did modify it here and there a bit to fit different carbs and the larger stud spacing on later heads. A friend of mine with two of the 50's Daytona bikes says the early ones like his were actually machined from billet, but a later one which I sold a bit back looked to be machined from a casting.