I think the 9660 may have come with 8.1 and a 9.0 but with identical power specs.
In any case, here are the 8.1 specs from Deere owners manual 9660 http://manuals.deere.com/omview/OMH215847_19/?tM= 9650 http://manuals.deere.com/omview/OMH175213_19/HX_AG_SF7252_19_01SEP9... I found the specs for 9660 9.0L here: http://manuals.deere.com/omview/OMH226957_19/OUO6075_0000375_19_24APR06_1.htm
 (9650-engine-specs.PNG)
 (9660-engine-specs.PNG)
 (9660-8_1and9_0.PNG)
Attachments
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 9650-engine-specs.PNG (25KB - 27 downloads)
9660-engine-specs.PNG (29KB - 26 downloads)
9660-8_1and9_0.PNG (37KB - 27 downloads)
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Why do 9660s have less HP than 9650s
