What should I replace

[Aproductions]

Okay so my engine was knocking and I just pulled the motor (it will be disassembled tonight). Do I have to get the crank mic'ed if the bearing didnt spin? This is on a 420a but it is a generalized question so it should pertain to all.

 

[crimsondragon]

You should do measurements every time a motor is torn down regardless whether or not it was knocking. Knowing the measurements will determine the life of the crank and whether or not its worth reusing. It'll determine the size of bearings to use though we don't seem to have much undersized bearing selection but the choice is yours whether you want to cut it down or not in case of extensive damage. It's also good to know the oil clearances as well.

 

[My1GLaser]

If it was knocking then you might have something out of round or with a flat spot depending on how long it knocked. (ie rod big end most likely, but possibly the crank journal) Even though your bearing in the other thread didn't look "beaten" its hard to tell over the internet and it could be off by .001-.002 and hard to see.

Have it mic'd!!! Take your time on a rebuild and you won't pay for a rushed job down the road. Like he said, knowing oil clearances will help you decide which oil viscosity to run instead of arbitrarily throwing 10w30 or 20w50 in there...