Anyone put a 650SS head on a 600cc?

Rob Hodder previously wrote on Friday May 4th at 23.10hrs:

Hi,

Anyone tried this? my brother has a '58 99 and has recently acquired a 650ss head.......................

Rob.

Hello Rob,

When you say the bike is now fitted with a post â59 head, do you mean it has the vertical ribbing between the rocker plates?

If that is the current head, the only difference between that one & the SS head will be the vertical manifold studs, on the 99 version and itâs narrower splay of the exhaust ports.

You are right about the SS exhaust ports having a wider splay than the 99, but the ports are the same diameter as far as exhaust downpipes are concerned.

No worries with chamber capacity. The final 50 or so 99SSâs went out with 650SS heads from Bracebridge St. So if it was good enough for themâ?â?â?â?. and you will find the headsteady will go straight on as well.

No fuel tank clearance problems.

There is another caveat though.

If your SS head is from post engine # 114870 (1966), it was made to fit barrels which had no cylinder spigots, where the cylinder sleeves protrude slightly above the head joint.

The recess on the head, at the joint face was correspondinglysmaller. So it won't fit the 99 barrels.

The belt & braces answer to fit the later head would be to have the spigots machined down on the 99 barrels, followed by the lightest skimming of the entire joint face. Those spigots become a nuisance after a couple of rebores anyway. As the cylinder sleeves becomes thinner, they split easily near the joint face.

If the head is pre-66, youâre laughing. Itâll fit straight on.

The inlet manifolds on the SS head will benefit from having the spring steel sleeves fitted, which ran from the guides through the manifold sleeves back to the twin 376 carb joint faces.

Although if you do go for a single (concentric 926?) carb and the manifold you use doesnât have too large a bore, that should give you good, torquey performance.

An Atlas manifold, at 1 1/8â would be much too big really, although it would work, just not very well.

Along with keeping the inlet manifold small, you will improve the torque by having exhausts which narrow (European 650SS style) after exiting the ports. I think all the US bikes went with large bore pipes though, and they were happy.

Benjamin Gradler has some good stuff for reference on his website:

http://www.facebook.com/pages/Norton-Manxman-SportSpecial-and-racing-motorcycles/187441501303123

If you dig around, I think he has some photos there of the inlet sleeves I was on about.

Maybe even some comparison pics of the earlier & later head recesses.

Les Emery will be familiar with what you are intending. I think he still does his telephone âclinicâ some afternoons. Check his Norvil website. I think he has details and times on his home page.

The 99 bottom end is not the strongest, so your brother is right not intending to ring itâs neck.

Later Commando followers, bevelled at the front will go straight in and encourage oil drain to the cam. Although if the originals are still in those barrels, Iâm sure thereâll be plenty of space for the lube to get through.

There yâgo.

Time I was off to the Z-Shed!

Paul

I have run my 99 with an SS head for more years than I care to remember. As mentioned, you do need the SS exhaust pipes. I have run both twin carbs and a single carb setup. It doesn't make any real difference to the performance. I eventually settled on a single carb manifold (too lazy to fiddle with keeping twin carbs in synch) and a 376 monobloc. I wouldn't worry about sleeving inlet manifolds for an exact match - the extra turbulence from any steps will give better fuel mixing and smoother running. Don't believe me? The BSA 350 Gold Star has the same diameter carb as the 500cc DBD34 but a smaller inlet tract and hence a big step. It was found at the works to produce more power that way. Strange but true. Gordon.

The early 99 is the worst choice to build for performance unless your brother has a large stock of extra engines which he can use up as he explodes them.

Tell him to enjoy the bike for it's fuel economy, touring and practical transportation as it is, which it is very good at. He can put the 650 head on a shelf and sell it when the bike needs funds for some heavy maintenance.

What documents have Norton putting 650 heads onto model 99s?

Hi Rob

There is lots of good positive advice on this thread and I would like to add a little more plus a tale of caution.

Back in the late 1960s, the Model 99 with an SS head on top of the barrels was the poor mans 650SS look-alike. So, unless you knew your Norton numbers there was no easy way of telling it apart from a real 650SS. Ideal for winding up any Bonnie owners passing nearby.

I owned three 99 engined Nortons that were fitted with the SS heads. The second one held together forover25 years and covered 95,000 miles. In that time span it only had one rebore andplus the mains changed once. The big ends were never touched.

My third bike has 'homebuilt' from well-used, spare garage bits and spent 5 years being thrashed around various 'track day' meets. Nothing ever broke and in its life itjust had one change of rings.

I bought my first bike, in CafÃ? Race form, from a âDunstallâ fanatic and used it to cover 10,000 miles of high speed commuting in just over a year. It was fast, reliable andeconomical but had been assembled with a small problem that eventuallyled to a much bigger one. The engine had been built using early dynamo 99 barrels and also the push rods from this model. These thin pushrods could not cope with the stronger springs in the SS head, an SS camshaft plus handfuls of high revs and eventually bent. This led to a need for replacement valves. At the same time a set ofWassell all alloy, SS style pushrods were thrown into the barrels. Bad mistake as they lasted less than a month. The pushrod tunnels in the early 99 barrels are too narrow to take the SS pushrods. They catch on the top lip of the barrels and also knock against each other. Eventually the sides get ground away and/or the top cups break up due to side loads they were not designed for. The answer is to use later barrels or get some machining done on the earlier type.

The 99 with the SS head, SS camshaftand single carbmakes a brilliant bike and seems to offer the best of everything. You can fit a single 928 carb but the 626 carb works better if you get the jetting right. Be careful as the 626 carbs come in 2 stroke and 4 stroke versions.

You can run the engine with the standard main bearings. There is actually no needto fitexpensive FAGs unless you have plans to go racing on it. However, if you do rebuild the bottom end, go foran uprated ball bearing for the timing side. Ask for MJBL30, M306 or a 6306 equivalent as areplacement.Keeping a ball bearing on theTiming side means no messing about with shimming to get the correct crankshaft float.

The 1960 and later Model 99, which might have the crank with the 5/8" sludge trap would be a lot tougher than the 50s bikes. That means that those cranks had 7/16" thick rod-journal walls! In comparison the older Dominator cranks with a 1" sludge trap had .250" thick rod journal walls, heading towards half the thickness.

Since it is not the 1960s anymore, and parts are dear and the old alloy Dommie rods have either unknown histories or many cycles of use, the person thrashing a 50s Dominator hard should take everything into account beforehand.

At 6000 rpm a lot of power can be had for "track days" and fast touring on roads, along with decent reliability. Above that engine speed for reliability you need the sort of person putting the engine together that does not need to ask others if the valve springs and other parts are good enough for the job.

There are truck-loads of old Norton twin cases from all cc displacements, laying around with old cracks, scars, welds or holes from bottom end failures.

Well then it will be interesting when he gets it running and you can add the results to the end of this thread, good luck.....

Hello you guys. Well - there was a twin carb model 99 back in 1958 called the Clubman, so people mistook it for a SS model. It went well and was fitted with two 376 carburettors at a splayed angle to each other. I had a 99SS from 1961 in cafe racer mode and it was one of the best bikes I have had in my time. So good luck with what your doing, ride safe. yours AJD

Previously wrote:

Thanks again for everyones comments. Nick has read the comments but is not currently a member so can't post, however the latest news from him is that the head is the spigot-friendly type, so an early one.

The current barrels on there are dynamo type, so they will be coming off to have the pushrod tunnels machined to provide adequate pushrod clearance.

He's currently running a 28mm Mk1 concentric, so that may well be used in the new set up as it should be adequate.

More news as it comes, he also has a dyno print out of the engine as it is now, so if we can get it scanned maybe I can attach it here.

I personally think it is a sweet running bike as it stands (1960 head, SS cam and rita ignition) , I've done some miles on it myself although not recently and I was very happy with the torque then, ( more than my standard '59).

Regards Rob.

Hello ROB **** 28mm Carb is a bit big for a 650 that's like fitting a 389 1.1/8 inch Monobloc YOURS AJD

928 works fine - at least it did for me for years. Why did I fit it? 'Cos it was cheap... Gordon.

Sorry Anna, you have got your sums wrong! 28mm= just a shade over 1-1/10". 25.4mm=1". John.

Previously wrote:

Sorry Anna, you have got your sums wrong! 28mm= just a shade over 1-1/10". 25.4mm=1". John.

Hello John To be very accurate its 1.1025 Of a inch . Yours Anna J

I think you should tell Nick to stop being such a tightwad and pay the relatively small subscription cost and join the club!

Colin.

Previously wrote:

Thanks again for everyones comments. Nick has read the comments but is not currently a member so can't post, however the latest news from him is that the head is the spigot-friendly type, so an early one.

The current barrels on there are dynamo type, so they will be coming off to have the pushrod tunnels machined to provide adequate pushrod clearance.

He's currently running a 28mm Mk1 concentric, so that may well be used in the new set up as it should be adequate.

More news as it comes, he also has a dyno print out of the engine as it is now, so if we can get it scanned maybe I can attach it here.

I personally think it is a sweet running bike as it stands (1960 head, SS cam and rita ignition) , I've done some miles on it myself although not recently and I was very happy with the torque then, ( more than my standard '59).

Regards Rob.

Previously wrote:

Just to resurrect this thread. Nick's bike is back on the road, with the refurbished 650ss head, barrel pushrods, 928 carb, Manifold ( should that be bi-fold??) from Norvil, header pipes from RGM.

It's going very nicely, although it did before, although now it seems a bit more rev happy. Maybe he will take it for a dyno run soon. Will post results if so.

The manifold was not very well thought out for gas flow - with a flat face welcoming the incoming mixture from the carb, it's been eased a little bit with Mr Dremel.

Regards Rob.

hello rob my manxmans is a bit of a rev happy bike with the 21 tooth Engine sprocket on , That why I going to fit the 22 tooth sprocket it cams it down a bit but still pulls like Big Boy .to any one who dose not know what Big Boy is well Its Only the biggest Steam locomotive ever built a 4-8-8-4 wheel arrangement, and four big cylinders for all that power they pulled trains 5 miles long , yes she big you can see these locomotives on You Tube well worth seeing ! it now takes 7 diesels to do the same job

Just keep the revs in the sensible zone - 99 rods are getting on a bit and can be a bit fragile. Bitter experience talking here.

Good to read that has worked out as I run something similar.

Anna, you mentioned the Union Pacific Big Boys. UP have rescued 4014 from the museum park where it has been stuffed and mounted for decades and intend restoring it for mainline running.

http://www.youtube.com/watch?v=OZbnKpW5h_M