Size of main bearing what one

[Marcus_penguin]

http://www.engine-dynamics.com/EngineComponents/pid688/cid111/CrankshaftMainBearings.asp

been looking at finally ordering bits for the engine build but it asks what size 0.25mm or 0.50mm
thing is iv thrown my old ones so would the 0.25mm be ok or would it be the 0.50mm

thanks for the help

 

[Snakebelly]

Has the crank been ground? does it need to be ground? not being negative but if your not sure about the relevance of oversize bearings is a full engine rebuild a good idea?

 

[Snakebelly]

And trying to be more positive this time.
If your crank journals have worn they will need to be reground, as the grinding process removes metal the bearings have to increase in size to take up the slack. Hence they are available in Standard, the size that would be fitted at the factory, 0.25mm oversize to take up the slack on what I have always referred to as a first grind then 0.5mm for a second grind.
What if any grinding will be required on your mains journals will be dictated by the amount of wear which should be measured in multiple points for each journal for diameter in several places across the journal to check for conical convex and concave wear.

hope that helps

 

[Marcus_penguin]

And trying to be more positive this time.
If your crank journals have worn they will need to be reground, as the grinding process removes metal the bearings have to increase in size to take up the slack. Hence they are available in Standard, the size that would be fitted at the factory, 0.25mm oversize to take up the slack on what I have always referred to as a first grind then 0.5mm for a second grind.
What if any grinding will be required on your mains journals will be dictated by the amount of wear which should be measured in multiple points for each journal for diameter in several places across the journal to check for conical convex and concave wear.

hope that helps

Right yeah that did make sense weirdly enough the bearings were fine but because I had the Pistons out I thought I'd change the beatings while I'm there, but I do understand what you meant cheers

 

[Snakebelly]

If your sure its the originals then they will be the standard size. If it was me and it was totally stripped I would spend the money and take it to a local engine builders just to get the mains and big ends miked up and ground if necessary.