Could someone help please?
Tim Gostling in the records forum was kind enough to identify my "hybrid" Dominator 99's engine by size and date of manufacture. Since it was made in October 1957 as a bog-standard 99 it has acquired a couple of SS stamps on the crank casing.
It is possible that there is nothing but misrepresentation (fraud!) about this but could the 1973 rebuild have included a sports cam? I have the cylinder block off the engine at the moment and, without taking the crankcase apart, the only real measurement I can make is the "rise" of the cams from the cam shaft itself. It is consistantly 8.5mm on one side of the cam and 8.9mm on the other across all four cams. (The shaft has different diameters; the cam surfaces are square!)
Attached diagram shows what I measured.
Is it possible to tell from this measurement if I have the standard cam shaft or is it something different?
Are there any identifying stamps on the camshaft that you can see? I do mean stamps, not casting numbers although that might help too.
"X1" or "X2" indicates an "SS" cam and "QR" (Quietening Ramps) is a Daytona cam fitted to 99s from about 1959 or maybe earlier, I haven't checked. It's probably listed on this site but I've started, so i'll finish this posting!
At 8.5mm as per your diagram it is very close to the special cam of the day that went on to become the standard cam we know today as the 06.1084. A cam so nice that it was re-introduced for the later Commando's as the standard cam.
NHT cams are either on twin chain (cam/magneto) core or later commando single cam drive chain version.While they have some dimensional similarities, they are not interchangeable.
22729 is the "SS", (on a twin chain core 1949-1970)
06-1084 is the "1S", (on a single chain core 1971-1975)
The grind profile is the same but will not interchange for mechanical differences between engine series.
Would like to borrow a "daytona" cam (pre QR) for profiling. TIA
Thank you for your replies. They have been most helpful and I now know that I have an early SS cam.
Casting number T2219@3 and stamped X2.
What a great resource this site is. I am much obliged.
Below is chapter and verse from last January.
Submitted by philip_hannam on Wed, 30/01/2019
The following info is taken from the unreleased Dominator Service Notes...........
There were four main camshafts produced by the Norton Factory for their standard Dominator engined bikes. All have the casting number of T2219. Those for the Model 7 engine are best avoided if the plan is to rebuild a post 1956 engine and expect a decent road performance from it. The first camshaft was right for the early ‘Iron headed’ engine, in that it helped to produce enough power without the top half over-cooking.
The later ‘Aluminium cylinder heads were able to cope with more power; especially those with the extended finning. So when the 99 engine arrived, with the ‘Daytona’ camshaft in 1956, this had extended times for valve openings, increasing the power, but also the valve train noise. The addition of a 0.010' ramp to its lobes, around 1959, to help quieten down the engine rattles. Hence the title of Q.R. camshaft. These identification letters generally being stamped onto its sidewall.
The fourth variation of the camshaft arrived with the Downdraft SS cylinder heads. (But was also fitted to the non-downdraft head used on the 99SS).
Basically it was the QR camshaft but slightly altered in profile and renamed as the SS. Most have a casting number of T2219@3. From 1960, this camshaft was a standard fitting for all the Dominator SS engines, including Atlas and Mercury. It even survived, in a modified form, to become a standard Commando part until ousted, for a while, by the arrival of the Combat 2S disaster.
The earliest SS camshafts were stamped with X1 (Bracebridge) or X2 (mostly from Woolwich). The X2 camshafts were supposed to have deeper hardening to cope with the 650 engines power but the late John Hudson claimed that the X1 version was produced with greater accuracy. Later Mercury camshafts often just have the casting number.
The SS camshaft will fit into any of the pre-1960 engines and run quite happily as long as excessive revs are avoided. Otherwise valve float can occur, especially above 6000rpm. But who (track day lads excepted) hammers an engine that much nowadays?
The attachment shows the four Dominator camshafts used in production bikes from 1949 up to 1969. The camshaft on the far right came from a very early Dunstall tuned 99. His later versions having the option of a fitted needle-roller bearing and positive oil feed.
It even survived, in a modified form, to become a standard Commando part until ousted, for a while, by the arrival of the Combat 2S disaster.
lobe grind was identical but the drive end was reengineered for a single drive chain and inboard tach drive gear was added.
"Basically it was the QR camshaft but slightly altered in profile and renamed as the SS"
This above statement needs to be corrected....
the Daytona was modified to become the(88/99) QR, the SS/22729 was entirely new see below
Also the SS cam in earlier (non SS) engines will need additional work, the 88SS had modified barrels to accomodate the valve train...99SS ?? I have no experience here...