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CP320
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I've rebuilt a few engines so aware of the cost which is why relining is preferred route as a I can keep pistons and just fit new rings.
Apologies Teflon if I sound frustrated, I'm not, I just don't understand how barring the engine over will get rid of those rust pits. If a gentle rub with some emery paper exposed them, then IMO scraping them with piston ring would also do the same.
Either way it would leave pits and comprise new rings.
I've now removed everything from the block and will try lowering it and sliding it under the wheel arch the next week. There's a machine shop nearby in Daventry that might be able to re-line. If worse comes to worse, there's a good used block on eBay for £230
I'm not an expert and have only rebuilt a couple of engines myself. My suggestion was based on the fact that you are unlikely to be able to remove the rust pits full stop but I think the engine will still run fine even with them present. My concern about the emery paper was that it would destroy the honing pattern. A sweep of the piston would remove any rust on the surface of the cylinder wall whilst not affecting the honing.
 

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Alan St500
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I know blocks are usually matched with the crank shaft ladder, or in this engine it's part of the lower housing as it's all bored as an assembly. If that's the case, it's fine as eBay block comes with it. But if it needs matching head or something else, then that's not good at all and will seriously screw things up.
Non ST - 2.5T S Max Engine Rebuild it’s in that thread somewhere bud
 

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2007 3dr Focus ST performance blue
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Its matched with the crank shaft ladder. Its safe to use another head or sump if you will have to. Equally important to not change is the camshaft cover as its matched to the head.
 

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2007 Focus ST3
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Discussion Starter · #26 ·
BTW, I lubed up the cylinders and barred it over a few times. There's still a very faint pit where the rust bubbles were but maybe I could get away with it?
Attached is latest pic 🤔
Automotive lighting Automotive tire Gas Circle Auto part
 

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2007 Focus ST3
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Discussion Starter · #29 ·
It looks bad but does it feel as bad or feel smooth? Turn it more and see if its getting better.
I feel a strong urge to fill that engine with CocaCola :ROFLMAO:
Nah, the pits feel a little rough. I'm wishing myself into believing otherwise but it doesn't feel right.
I'm gonna remove the block anyway and take it to a machine shop to see what they think but my gut feeling is it needs relined or replaced.
 

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2007 Focus ST3
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Discussion Starter · #30 ·
Bit of a lucky escape with the crankshaft and piston rods. They too are turning rusty but luckily, where it matters (bearing seats), the air's been kept out and they're nice and clean.
 

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I would have given the cylinders a good coating of oil and turned the engine over by hand a few times to sweep the bores with the pistons, then ensure a thin film of oil was left to stop them rusting up again anytime soon.
Thats far worse! The rust will likely be dragged up and down causing vertical scoring and damage to rings and pistons. The only course of action is a light hone or carful diagonal rub down with fine abrasive medium. Trouble is you cannot see or get to lower bores. But once rusting has caused pitting, the bore is really none serviceable. I would not be happy using those bores anymore, Will likely have blowby issues.
 

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Thats far worse! The rust will likely be dragged up and down causing vertical scoring and damage to rings and pistons. The only course of action is a light hone or carful diagonal rub down with fine abrasive medium. Trouble is you cannot see or get to lower bores. But once rusting has caused pitting, the bore is really none serviceable. I would not be happy using those bores anymore, Will likely have blowby issues.
If it was heavily rusted up such as having had pools of coolant left in cast iron lined cylinders for months then you might be right, but the rust in the photos is really no different to what forms in any engine that is left for some time without running. Provided there isn’t any significant damage these engines will almost always start up and run fine, and at a much higher speed than turning over by hand.
 

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If it was heavily rusted up such as having had pools of coolant left in cast iron lined cylinders for months then you might be right, but the rust in the photos is really no different to what forms in any engine that is left for some time without running. Provided there isn’t any significant damage these engines will almost always start up and run fine, and at a much higher speed than turning over by hand.
Cylinders do not normally rust when the engine is standing, not for a bloody long time after the oil film has eroded. I’ve opened engines stood for 40 years without any sign of rusting. Any rusting is pitting, the longer it stands the deeper the pitting will get. You do not want any pitting on bores and certainly none you can feel or easily see. Yes it will run, that means nothing, but the combustion gases will leak past the rings in that pitting eroding it further and in extreme cases able to blow by the rings and cause flutter, that can destroy the piston in seconds. You certainly never want to force pistons over a rusty bore! I have rebuilt many dozens of motorcycle engines and a number of car engines and learned the hard way that bore quality is critical especially on high performance engines. It’s not just rust and pitting, clearance, ovality and taper are also critical and should be measured accurately whenever you think of fitting new rings or continued use of old bores. New rings in an old worn bore is usually a very bad idea.
 

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2007 Focus ST3
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Discussion Starter · #34 ·
Just took the head to a machinist and it had warped an eye watering 0.5mm, so the chances are the block will be just as bad so they're both scrap :-(
Anyway, looking at a used head and block from ebay tomorrow which looks tidy enough :)
 
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