Discussion and questions related to the course Practical Engine Building
Hi guys/andre i have a fiesta st180 came into the workshop for a misfire turns out the lad had the piston burnt out the side of the piston. A reflash map might have been cause and also he mentioned could i drain his fuel and add super unleaded i assume by this he might have thrashed it on normal octane fuel. Anyway has anyone got any kind of links or help or info on this model as there is no manual. Tech specs info for rebuilding. Andre on the main bearings there is some light scoring in 1 half of the bearing? Debris from broken rings and pistons and shock loading the cylinder head checked out ok and machine shop only 1 piston suffered what your thoughts
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.