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Crankshaft runout

Engine Building Fundamentals

Discussion and questions related to the course Engine Building Fundamentals


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Please how it is with crankshaft runout? What is the acceptable and what is the minimum runout? Should it be 0,00?

Thank you for helping!

Ideally there should be zero run out. If you check the workshop manual for your particular engine there will be a maximum allowable specification for run out.

Manual says max run out 0,2mm which is pretty a lot - it is M52B28 crank. Right now there is about 0,04 run out measured just on the table crank supported by ball bearings on the outside bearings. Should I do measurement in the block clamp crank at first and last bearing? Thank you

0.2 mm is getting on towards 8 thousandths of an inch which is more than I'd tolerate in a performance engine. Your 0.04 mm is more in line with my personal targets and you shouldn't have anything to worry about, particularly with a long crank like an inline 6 cylinder where there's inherently more likelihood of sagging. It is important to make your measurements the right way though. I support the crank in v blocks on the front and rear main journal and then use a dial indicator on the centre main.

Yes, thats what I thought. Thank you very much!