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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Pazon Sure Fire
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<blockquote data-quote="timetraveller" data-source="post: 25492" data-attributes="member: 456"><p><span style="font-size: 12px"><span style="color: #000000"><span style="font-family: 'Calibri'">It is not just the number of spark plugs which is important but also their position. Vincent and original Manx Norton heads with high compression pistons have a fairly awful shape. If the plug is off to one side then the flame front has to travel a long way and over the bump in the middle (the piston crown). Tom, like me, is old enough to remember all the experiments in the fifties by the best tuners at the time into swirl and squish. Several years ago I happened to see the cylinder head of some bog standard small Japanese car (I think that it was a small Nissan) and was surprised to see just how much swirl and what huge squish bands were built into this non sporty engine. The difference which can be made by incorporating such items into a Vincent engine is remarkable. Several years ago I was helping Roy Robertson at Brands Hatch and was going to move his bike to a different part of the paddock. I made a total prat of myself be stalling the engine three times while trying to gently let the clutch out at 2,000 rpm. The bike would produce about 100 h.p. flat out and yet at 2,000 rpm there was only about enough power to keep the engine ticking over. Later Roy fitted Terry Prince cylinder heads which have serious squish bands. Top end power is about the same but at the bottom end the bike is like a traction engine. The turbulence in the combustion chamber, created by the squish bands, also ensures that for road use a compression ratio of about 10:1 can be used without the unpleasant side effects that would generally occur with the original combustion chamber shape. Perhaps I should say that I have no financial connection with Terry Prince but did provide him with the copy of the ‘George Brown’ fairing which he uses to such good effect on his outfit.</span></span></span></p></blockquote><p></p>
[QUOTE="timetraveller, post: 25492, member: 456"] [SIZE=3][COLOR=#000000][FONT=Calibri]It is not just the number of spark plugs which is important but also their position. Vincent and original Manx Norton heads with high compression pistons have a fairly awful shape. If the plug is off to one side then the flame front has to travel a long way and over the bump in the middle (the piston crown). Tom, like me, is old enough to remember all the experiments in the fifties by the best tuners at the time into swirl and squish. Several years ago I happened to see the cylinder head of some bog standard small Japanese car (I think that it was a small Nissan) and was surprised to see just how much swirl and what huge squish bands were built into this non sporty engine. The difference which can be made by incorporating such items into a Vincent engine is remarkable. Several years ago I was helping Roy Robertson at Brands Hatch and was going to move his bike to a different part of the paddock. I made a total prat of myself be stalling the engine three times while trying to gently let the clutch out at 2,000 rpm. The bike would produce about 100 h.p. flat out and yet at 2,000 rpm there was only about enough power to keep the engine ticking over. Later Roy fitted Terry Prince cylinder heads which have serious squish bands. Top end power is about the same but at the bottom end the bike is like a traction engine. The turbulence in the combustion chamber, created by the squish bands, also ensures that for road use a compression ratio of about 10:1 can be used without the unpleasant side effects that would generally occur with the original combustion chamber shape. Perhaps I should say that I have no financial connection with Terry Prince but did provide him with the copy of the ‘George Brown’ fairing which he uses to such good effect on his outfit.[/FONT][/COLOR][/SIZE] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Pazon Sure Fire
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