Well Ive finally stripped my 650 engine I acquired. Ive measured the big end journals and the main bearing journals. They big end journals are both 1.732" and the main bearing journals 2.124". Is this fine or does it need a regrind?
Technical Crankshaft dimensions
- Thread starter JonPiz
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Technical Crankshaft dimensions
the hobbler
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the main journals on all the 126 crankshafts are between:---- 2.1256 in (53.990mm) and 2.1248 in. (53.970mm).
big-end journals are between:---- 1.7336 in (44.033mm) and 1.7328 in (44.013mm) From the measurements that you have supplied,I would suggest that you have the crank ground. Have a word with your local machine-shop, see what they recommend vis-a-vie what shells/bearings are available before you buy anything.
Ive taken the crankshaft to my local engine workshop and it needs to be ground. What are the dimensions for a undersize by 0.4mm grind on both the main and big end journals please
the hobbler
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Time to get the calculator out, but your machine shop should be able to tell you what size the journals will reduce to. A word of warning--BEFORE you get the crank ground, make sure that the appropriate under-size bearings are available. MOTOBAMBINO has +o.4mm undersize MAIN bearings but only .25mm and 0,5mm undersize big-end bearings
For whatever reason Fiat decided to measure the main bearings in metric and the big ends in imperial but it is quite easy because give or take a gnats eyelash 0,25mm equals 0.010”. If your machine shop, who really should have the tech specs by the way, are talking 2nd undersize on the crank journals then that is 0,4mm (0.016”) on the mains and 0.020” (0.5mm) big ends.
Thank you
