I'm not convinced about the accuracy of the various figures. For example, if you do the arithmetic on a 1071, you get 1069cc. BMC might have rounded this to 1070, but surely not to 1071?
1380?
Started by
nath
, Apr 14 2011 03:26 PM
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18 replies to this topic
#17
minikidx14
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One Carb Or Two?
- Name: Ross
- Location: Weston-s-mare
Posted 15 April 2011 - 09:25 PM
#19
Cooperman
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Uncle Cooperman, Voted Mr TMF 2011
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Posted 15 April 2011 - 09:46 PM
I'm not convinced about the accuracy of the various figures. For example, if you do the arithmetic on a 1071, you get 1069cc. BMC might have rounded this to 1070, but surely not to 1071?
Who will ever know what BMC did to get those figures. The A-series was designed and drawn using inch measurements, so already they have been converted to metric.
If you have ever measured the accuracy of crankshaft throw you will know how far out they actually were, up to around +/-0.004".
Maybe the capacity quoted is the maximum you can get with all the tolerance considered. 2 x 0.004" on the stroke would add about 1 cc to the swept volume. Add a maximum bore tolerance and you could get a bit more.
Oh, the wonders of 1960's manufacturing technology.
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