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General Chat (Vincent Related)
5 Speed Gearbox
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<blockquote data-quote="Black Flash" data-source="post: 738" data-attributes="member: 433"><p>Hello Mick, I have just received my engine back from Bob Dunn. It had the same treament as yours, bored stroked, 36 mm carb, MKII cam and so on. When I spoke to him about the gearing, he told me that I have to increase the size of the g/box sprocket by 3 teeth for a start or maybe 4. He told me that the engine has so much torque that increasing the overall gearing by 20% will have no effect on acceleration as the engine doesn't built up speed fast anyway due to the long stroke of 100 mm. His words really make sense to me and with a gearing about 20-25% higher you should get enough terminal speed without the need of a 5 speeder. You should also keep in mind that the engine should rev a bit when cruising to dampen the power pulses of this big bang engine in the poor old Burman gearbox. I am just building another Comet special with a Terry Prince 600 cc topend and use an AMC commando gearbox with special machined lugs, possibly the strongest of all the english gearboxes. If you fit one of these Commando boxes, there is no need to machine the primary chaincase as the mainshaft is longer than on the earlier AMC boxes(ie. Atlas). as much as I know there are drawings for Converta engine plates in 40 years on or some other publication, I am sure they were in MPH yaers ago, but you can certainly ask Ben Fietje, cause he is using this conversion on his racing Comet.</p><p>Hope I could help you a bit</p><p>Bernd Schmitz "Black Flash"</p></blockquote><p></p>
[QUOTE="Black Flash, post: 738, member: 433"] Hello Mick, I have just received my engine back from Bob Dunn. It had the same treament as yours, bored stroked, 36 mm carb, MKII cam and so on. When I spoke to him about the gearing, he told me that I have to increase the size of the g/box sprocket by 3 teeth for a start or maybe 4. He told me that the engine has so much torque that increasing the overall gearing by 20% will have no effect on acceleration as the engine doesn't built up speed fast anyway due to the long stroke of 100 mm. His words really make sense to me and with a gearing about 20-25% higher you should get enough terminal speed without the need of a 5 speeder. You should also keep in mind that the engine should rev a bit when cruising to dampen the power pulses of this big bang engine in the poor old Burman gearbox. I am just building another Comet special with a Terry Prince 600 cc topend and use an AMC commando gearbox with special machined lugs, possibly the strongest of all the english gearboxes. If you fit one of these Commando boxes, there is no need to machine the primary chaincase as the mainshaft is longer than on the earlier AMC boxes(ie. Atlas). as much as I know there are drawings for Converta engine plates in 40 years on or some other publication, I am sure they were in MPH yaers ago, but you can certainly ask Ben Fietje, cause he is using this conversion on his racing Comet. Hope I could help you a bit Bernd Schmitz "Black Flash" [/QUOTE]
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5 Speed Gearbox
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