Discussion and questions related to the course Practical Engine Building
I'm sorry the ST180 isn't a car/engine I'm overly familiar with. I've had a very quick google and haven't found anything specific, although I'm convinced a little more work would uncover some info given the engine's popularity. It does appear that haynes produce a workshop manual that provides tech specifications so that may be one avenue to go down.
It's not uncommon for the bearings to show some sign of distress in an engine that's seen a failure like this. Assuming the crankshaft journal isn't damaged or can at least be polished, and the rod isn't bent, it shouldn't be a big deal.
Turns out the bore also was cracked not seen on intial strip down so the oversized piston and boring is out the window now. We had to order in a new bare block and start from scratch yes the crank was ok a polish up would do. This might seem like a stupid question but can i ask if the bearings are scored but there is a bed of oil between the crank and journal what implications does it have if the oil stops them touching anyway ? Even if there is scoring what does it actually do thats a problem ? Oil cant flow or trap dirt etc?
If the bearings are showing signs of scoring then it's likely that there has been metal to metal contact at some point, or at least a reasonable amount of debris has been passing through the oil. Light scoring is probably going to have little effect on engine operation. Heavy scoring though can mean there is enough wear to affect oil clearances and if these become excessive you can find the damage will quickly become worse in operation.