NHT domi cam

Hello Dave - I have part number 21225 for an 88 ,99 Std and De-Luxe in 1961.  It does not mention QR on the part number but by then I suppose they only made that version.  Good luck with your searching. howard

According to my chum,  John Hudson,  the QR cam timing figures are 49/77/79/47  and the first SS cam is 50/74/82/42  both using 13thou checking clearance. Getting the inlet opening to lead the exhaust closing by 8 degrees on the SS cam on both cylinders may need a little juggling with valve clearances, Doing the same on the QR cam may be a bit more challenging.  I have included the Race Shop data sheet for the 1955 Daytona Race camshaft .  I can't see a part number anywhere so it may be that the race shop modified the grind from a standard casting blank.  Regards, howard

Comparing the Daytona ramped cam as fitted to slimline 88/99 s and the  figures supplied by Howard for the early race cam it seems to me they are the same cam but just fitted with ramps to silence the clattter . The Early cam was probably fitted with radiused followers too instead of the flat ones for the slimline bikes .

Factory books as  supplied to dealers in the Uk and USA have been saved  and I have access to a  good  selection , however its  pretty much all for  road and off road bikes as retailed to the public.  The twins in the 50's  were not seen as racers and very few special parts were made for them . The Nomads, Daytona racers plus the odd scrambler/ISDT  mount  was  about it. I doubt that it was worth printing books. I will look though.

Seems likely that the Daytona "race " cam  was copied from a  Triumph or BSA  racy profile (they did that sort of thing!)  and only got called Daytona after it proved itself in competition at Daytona. Then add some ramps  and use it as a selling  aid.  Its wot I would have done . I'm thinking of changing mine  to a  650 SS cam  so i can  get a little  better breathing.  But I wont be changing anything else (pushrods ,springs etc.) .   I never did follow the rules !. 

I will be swapping out a Daytona cam for a 650 one and retaining the std alloy pushrods which are a bit slimmer i think. , i can grind out a bit of the tunnels if needed.. The revs I use will not stress out the parts anymore than the Daytona cam could and I wont need harder springs etc. Valve clearances will be tailered  to get the best valve timing on both cylinders . Its all a  bit of an experiment. I may lighten the valve gear to allow the softer springs to remain  . There will be some work on valve seat angles to improve airflow at small openings . Inlet tracts and chambers  will be cleaned up and volumes equalised . Not tuning for speed,  more just making an efficient smoother  engine. Its pretty good already and can do over  100mph or 100mpg  (proper gallons that is !) and idle very slowly and evenly. I rarely get to 80 mph these days. No need at all.

Can't say for sure, but its the sort of thing that  John Hudson  carried around in his head. Or possibly Phil Hannam.