Norton 88SS Cylinder Head

I have seen the SS marking on barrels and assumed that it was perhaps because the barrels had been selected because they were on the plus side of std bore and would stand harder use with an extra thou or so of clearance (as recommended by J.Hudson for performance motors). The heads may have also been selected for similar reasons IE better port finish , alignment with stud holes etc. The stamping does look factory. I built a fake 88SS once and it was a great bike.

Here in north america we do not have a lot of 88 or 88ss. That has not stopped me from researching the subject with both norton factory parts books and limited on hand components. My research shows the following and is what I currently hold as true. 61 were the early 25mm/low intake port head. Norton p/n 88SS/136

The 62 88SS version had the S650/136 head. It also had the 650SS/atlas/commando cam/pn22729.

The 88SS had barrels that were marked as SS because the lifter bore for the EXHAUST was specially cut to prevent the pushrod from hitting the forward edge of the barrel tunnel. The exhaust rocker arm is in the front of the head and the now high lift cam causes the push rod to follow the short rockers swing. There is also an evolution of push rod style that likely contributes to the clearance requirement. Any other stated reasons are less important or fictious.

I own several 500 barrels and the SS difference is quite clear to me.

Cylinders should always be designed and fabricated to a nominal bore. The required clearance should always be machined into the piston.

I'd offer that the SS stamped on the non downdraft head may mean it has 1.3"exhaust and 1.4"intake. Early heads were 1.3"/1.3" (not 100% sure when they changed)...hard to verify here in the USA.

Adding a little more information, from my own records, to Daveâs comments.

The fifth generation of the Norton twin cylinder head arrived on standard production machines in 1959. Though it had already previously been tested out on the first of the Nomad Off-Road Specials a year earlier. It has casting number 22707 near the inlet cover and was generally fitted to 500cc and 600cc engines until the end of 1962. It has slightly increased finning all over but especially in the exhaust area. Plus the finning pattern in front of the spark plug was now all horizontal. A very noticeable feature of these heads is a line of raised cross ribbing between the two rocker spindle covers. All of these heads had the larger inlet valves of 1.406â diameter and the compression ratio had risen well above 7.4 to 1 depending on model. But matching those fitted to all the early SS models. Stellite-tipped valve stems were also now the norm. These 1959-62 head also had carburettor manifold mounting studs with 1 5/8" vertical centres as opposed to the earlier 1 ?â of the earlier versions.

In 1960, the first versions of the legendary semi down draught SS cylinders heads appeared. These were significantly different from the earlier heads and caused much confusion in the chronology of Norton engines. They first appeared on export-only 650 engines and later on the 88SS bikes. However, they were not standard on the 99SS bikes, early 88SS bikes or any of the Nomads. The two most radical changes were the revised angle of the exhaust ports and the carburettor manifold mountings. The latter now consisting of 4 horizontal studs.

My notes suggest that around 150 Model 88SS bikes were built with the old 22707 head at the beginning of 1961. These heads had a special twin carb adapter to suit the head and was a part again found on the Nomad engines or available from the factory as an extra.

The use of these cylinder heads may have been down to priority for of the SS head being given over to the 650 engines. Around April of that year, the 500cc engines gained the proper SS head whereas the 99SS launched at the same time kept the earlier head and twin carb adapter.

Once of the biggest causes of confusion is the fact that the pre-1961/62 single carb heads had the same 22707 casting number as the later 88SS and 650 cylinder heads.

1956-58-cylinder-head-jpg (51.3 KB) is R12/136

Cylinder Head 1959 to 1961.jpg (65.1 KB) is the 88SS/136

http://atlanticgreen.com/images/650sss.jpg is the 650SS/136

I don't bother to try and identify heads by a partial casting mold number such as 22707 since they are not necessarily unique to a particular head.

Folks that rely on the mold number have gotten burned buying the wrong head.

By 63 some (I've seen two) of the S650/136 head had lost their 22707 skull mold number.

http://atlanticgreen.com/nhth.htm this web page has been in research and up date for 18 years and while it could be presented better, I find less and less updating necessary. Phil has contributed a lot to it...thanks

As the early 88 and88SS heads were visually identical with the same valve sizes then the difference may have been the fitting of multirate valve springs to cope with the SScam.

Robert you are very likely to be correct. Most of my early heads were really butchered with wrong components, so my existing old equipment in this respect is not to be trusted as correct.

The actual valve weights (1.3" 1.4" ) do not differ enough to warrant a spring change but the model 7 cam and early 500/600 cam are mild compared to higher lift 22729(ss). It almost seems the 500 (1.4 intake) with a SS cam as being much hotter compared to a combat cam in a 750, therefore the upgraded springs.

All the cam profiles are also posted on my site...

The Norton operation at Birmingham was really very small compared to other factories (although profitable when AMC was not!) , The numbers of 88SS bikes going thro probably would not have warranted a seperate production line, so it would have been essential to be able to differentiate between parts that looked identical but were not. Hence SS stamping?.

Hi Jon - It looks excellent and there is nothing wrong with those late big-valve heads. Both the 99SS and 88SS were giving excellent performance employing them in the very early sixties. The factory manifold was the weak link but not with your splendid modification. Great work. The 88SS is the best Dominator ever built. Cheers, Howard

hello to put a few thing right here the Nomad did not have stud mounted carburetors like the early clubman twins from 1957/8/9 the nomad had a snub fitting for pre mono block carburetors 76gy/1a and 76gx/1a and there is no such thing as a SS cam just because the Manxman camshaft and its followers and push rods and a set of crankcases were fitted to the first 500 sports specials from april 1961 along with the model 99 sports special but the Norton Manxman 650 was the first to have fitted the down draft cylinder head with casting number 22707L other cylinder head have the same cast number but marked with a different cast letter at the end, the First Norton Manxman 650 was built from november 1960 and by august 1961 the model had changed to sports special 650s and the cylinder head photoed may well be from a 650 manxman model and twin carburetors were fitted as far back as 1953 to the model 88 modified for racing as I have a set of race manifolds has my model 88 was raced at pebble beach it was bought by me with race parts fitted including a manx race tank and seat and rearsets and race sprockets , all now standard sized and standard trim and now running very nice with easy starting

yours anna j

Here we go again - another thread about to be ruined by the history of the Manxman. This thread was all about the early 88SS - who cares about Export only 650's. i am out of here. Cheers, Jon

PS If any of you newer members or readers are interested in the Sports Special models have a look at the closed thread started by Ms Dixon on 28th November 2013. Cheers All.

I would be cautious about reading anything into stampings on cylinder heads - or any other part. People like to stamp things.

Jon

Seeing the rest of the head it seems to have started life as a 88ss/136 and heavily tig welded to make it into a custom low port S650/136 styled head.

True the meaning of the ss stamped on your modified 88ss/136 head eludes me, since we have so little of this equipment to examine here...but with hundreds of these heads in England you guys have not reverse engineered the meaning either.

Or if someone knows they are not telling!

The reality is that there are few genuine 88ss machines out there. Many would have been turned into 650's or tritons. I see more late DD head ones than the splayed head versions.

In near 20 years I have only ever met one more 88SS going the same way as me. He had the earlier head. And was certainly no slower than mine. .I'm sure the cam gave more benefit than the downdraft head but it wasn't anything like a blind trial.

On the subject of stud arrangements. I found out when I put twocarbs on mine ( PO had fitted one...) that there are three studs with nuts plus one Allen screw because there's no room for a spanner on the last one of the side by side pair in the middle. I imagine Commando is the same?

Now I look at Jonathan's photo and I see four nuts in a row. Was I misinformed or will he have problems assembling it?

David

Not sure what Jon is going to do...his nuts appear to be thin wall like the commando alternator stator nuts maybe cycle instead of UNF?

The curved manifolds on the commando use entirely different hardware.

My faux 62 88SS has a 22729 cam with S650/136 head and I will use 2 studs and 2 long allen screws like my friends manxman.

What cam?

per Anna "and there is no such thing as a SS cam"

I had always heard the 22729 cam refered to, at street level, as the SS. It is however often confused with the combat 2S since the cam is stamped with SS.

it can all be sorted here: http://atlanticgreen.com/camsurvey.htm

The twin chain core SS profile is the same profile as the 1S 06-1084 single chain commando core.

Previously howard_robinson wrote:

Here we go again - another thread about to be ruined by the history of the Manxman. This thread was all about the early 88SS - who cares about Export only 650's. i am out of here. Cheers, Jon

Hello well if you care to read the thread you may find that the 500 sports special engine was made with parts from the Export 650 manxman And there are 58 owners I found out there and they care and so do I. No matter what this machine is still apart of Norton History Like it or not this show you have very little in the way of interest of Norton motorcycles from Bracebridge street workshops , so why make comment in the first place, good day sir, yours Anna J