surfblue63 wrote:I wouldn't have thought that those Amals from the Norton would work. They are from a twin cylinder 850, not an in-line 4. Surely the air velocity per intake stroke would not be high enough for them to work. The air volume per intake in the Mini 848 would be half that of the Norton due to having twice as many cylinders.
Surely an 850 is an 850...?
The nortons twin would have a bigger intake, but only once per revolution, as one is on exhaust as one is on the draw... The mini's 4 stroke would have more intake per revolution as the pistons are staggered better?? One drawing, one compressing, one being fired and one on exhaust... Would it not make for smoother running? Weren't the Nortons rubber mounted because of the way the engines were? The later Jap stuff had the cranks 180 out and cut down on the vibration, I think Harleys used the rubber mounted idea on their Vtwin...?
My chum had an old mate Bill G who worked at Abingdon back in the 60's (engineer+special tuning). They had several mad lash ups. One of the blokes had a 1275s and another had an 850 mini with an aeroplane cabin blower (roots supercharger) in the PASSENGER FOOTWELL. From what I remember, it was considerably faster than matey's cooper s, as well as some Triumph with a V8 engine which was a lash up. I remember a comment about something transmission lasting about 2 weeks and there being loads of fuel in the oil and them having to keep changing the oil. However, it was the fastest mini at abingdon for a time. I think it got sold to someone who crashed it.
So, 202 head, or a 1098 head and a floor mounted blower.
British parallel twins are pretty interesting. The pair of pistons move up and down together, so they have a lot of combined inertia. The result is that they tend to vibrate like a bastard. My Triumph will shake the fillings out of your teeth, after a long ride your feet tingle from the vibrations through the foot pegs. The engine note is pure mechanical music though.
When the new Triumph developed their retro styled Bonneville and Thruxton they had to keep the pistons together to maintain the exhaust note. To get rid of the vibrations they added a pair of counter balance shafts. Apparently they work pretty well.
The nortons twin would have a bigger intake, but only once per revolution, as one is on exhaust as one is on the draw... The mini's 4 stroke would have more intake per revolution as the pistons are staggered better?? One drawing, one compressing, one being fired and one on exhaust... Would it not make for smoother running?
Granted, at higher revs this would be OK, but at lower revs the intake is more of a pulse, so the air velocity on the 4 cylinder would be less per cylinder intake.
What type of Amals are they 930 or 932 as 850 Commandos had both fitted? The 930 has a 30mm choke and the 932 is 32mm.
I did a bit of diggin on the web and found these which may help
I was aware of the two sizes, Mine are 930's... I cant see this being a problem, seeing as though the 850 had the HS2 as a single which would be 31.75mm... so two at 30mm should be an advantage...
I may find that like mark I cant stand them, and I slap on some twin HS2s... But I'd like to give the Amals a go!
