99SS valve spring lengths

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.

Anna, a Model 99 Norton that will keep up with a Suzuki GS1000? Okay.......

It is possible. All you need is Anna's cafe racer 99, a whole bunch of GS 1000s and a very long drop. They should all arrive at the same time... Sometimes I can be so cruel.

Previously wrote:

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.

Hello Well He may Call me a Back yard mechanic too , But he Would Be lost On a 300.000 ton Ship Engine ,like a Stork or Doxford or a H&W Or a Suzler And that just a few ,Now would he , He get lost in the engine Room there that big ! the main tools in there is a 400 ton gantry crane, and a 6lb hammer , yes this is REAL Big Boys TOYS

I shouldn't really rise to this but my professional big boys toys would potter along at 600+ knots. A bit faster than Anna's ships, and definitely faster than a 99 cafe racer or a GS1000.

Previously wrote:

Well I shouldn't rise to it either, but I was at one time responsible for the maintenance of several MWM 10MW marine diesel engines. The top speed was well documented to be precisely 0 knots.

They were, and probably still are, in the power station of Al-Zilfi and Skirts in Qassim, north of Riyadh.

Is this off topic?

Steve

Hello Steve MWM are a very good engine , Have you seen a Stork Marine or a Doxford Or a Suzler Marine or a Jolsko Swedish Two stroke Diesel like a Newbury marine

Before you drop it, my favourite diesel engines and they're 2 stroke!Royal Scots Grey

The books say that the first 88SS (about 80 or 100 bikes) had the 'non-downdraft' head. i.e.'factor non-downdraft twin carb.

I encountered one once (VMCC relay ralley - at Aldermaston) and thought it was a made-up standard. I was wrong (as I found out later). I chased it on a long dual carriageway on my own 88SS (downdraft head) - and I was upset to find he was running at 80mph++ a lot more easily than me. He was bolt upright and I was flat on the tank. I have since measured my cam and I think the PO changed it to standard (.030 not .033lift) - but anyway it made me think that there might well not have been the benefit in changing the head that they advertised at the time. A sharper cam works wonders more effectively than a different head, it would seem.

Also he had 'proper' monobolcks while I have inferior Concentrics (for historical reasons...) (Dunstall says the Monoblock was better - and it has a cleaner hole so it should be).

Mine has beautifully polished inlets - which we now know is not a good idea. And, wierdly, I thought Norton discovered that nicely polished inlets weren't a good idea - back in the 1920's when a new head casting allegedly wrecked the performance of the 16H Brooklands Specials...

The books say that the first 88SS (about 80 or 100 bikes) had the 'non-downdraft' head. i.e.'factor non-downdraft twin carb.

I encountered one once (VMCC relay ralley - at Aldermaston) and thought it was a made-up standard. I was wrong (as I found out later). I chased it on a long dual carriageway on my own 88SS (downdraft head) - and I was upset to find he was running at 80mph++ a lot more easily than me. He was bolt upright and I was flat on the tank. I have since measured my cam and I think the PO changed it to standard (.030 not .033lift) - but anyway it made me think that there might well not have been the benefit in changing the head that they advertised at the time. A sharper cam works wonders more effectively than a different head, it would seem.

Also he had 'proper' monobolcks while I have inferior Concentrics (for historical reasons...) (Dunstall says the Monoblock was better - and it has a cleaner hole so it should be).

Mine has beautifully polished inlets - which we now know is not a good idea. And, wierdly, I thought Norton discovered that nicely polished inlets weren't a good idea - back in the 1920's when a new head casting allegedly wrecked the performance of the 16H Brooklands Specials...

Interesting you should mention highly polished inlets. When the inlet charge is facing an adverse pressure gradient, i.e. when the piston is past BDC and the inlet valve is closing, it needs an energised boundary layer to prevent flow breakaway - and that comes with a roughened inlet tract surface. So to get the ultimate cylinder filling, don't have highly polised inlet tracts. Gordon.

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