An engine with a broken timing chain raises a few questions. First of all - why did the chain break in the first place? That really should happen. I'd expect to find the the chains themselves knackered (obviously), severe damage to the guides and tensioners and potentially to the sprockets too - both crankshaft and camshafts.
I'll admit I don't know the routing of the oil galleries on the Duratec very well - the chains are wet though so as a minimum the sump will be full of debris. Let's be optimistic and assume that there has been no scoring damage to bottom end from fragments in the oil. The high pressure stuff like the actual crankshaft main bearings and big ends is filtered first, but it's possible debris has been caught between a conrod and a crankshaft counterweight and scored both.
Damage consequential to a timing chain failure would include, as a minimum, bent valves. Bent valves often stuff their valve guides, and in extreme cases I've heard of cast camshafts fracturing or indeed the cast aluminium caps or the heads themselves fracturing or cracking under reactions to valve-piston contact. Onto the pistons themselves; I've seen as little as the carbon being knocked off the piston crowns with no damage to the pistons themselves (this was an early 90s Renault engine that was only just an interference engine, and the timing belt broke on start up, so it was doing tens of RPM at the time, not thousands. I've also seen pistons with holes punched clean through the crowns with or without the valve head broken off and embedded in it. Sometimes, and possibly more dangerously, I've seen pistons which kinda looked ok but had cracked around the crowns or ringlands. If you were a bit gungho you could carry on and build the engine, only for it to fail spectacularly shortly afterwards.
I'll be honest with you - I've only stripped and rebuilt a couple of car engines. I've stripped and rebuilt quite a few for light aeroplanes though, some of which were automotive conversions. Others who do this for a living can feel free to correct me if they disagree, but in general I think it's fair to say that most engines can be rebuilt if they're stripped and rebuilt as soon as an observant operator notices they aren't running right. When an engine is run until it no longer runs, in my experience that tends to go hand in hand with there being very little left in a useable state afterwards. That's less true with something like an air cooled VW for which you can literally buy any component new with ease. I think it's very true for an engine like the Duratec for which the manufacturer is unwilling or unable to provide spares backup.
Assuming you can get replacement components, with engine rebuilding you always have this chicken & egg period of having to commit to machining work to see how much you need to grind the crankshaft down by, or the cylinder bores out by before you know which undersize of bearings you need or oversize of pistons you need. Before you can start machining though, you need to know which undersizes of bearings and oversizes of pistons are even available. Getting STD size parts for the Duratec is hard enough.
Parts
are available. Not all of them, but I know bearings are. I don't know where from, but I know others such as charliecd001 on here has rebuilt a few of these so he must have a source.
I'm just cautioning you on the folly of buying a non-runner. If you're sure you know exactly what's wrong with it and you know them and the parts catalogues inside out then you may get a bargain. Chances are, most folk will get a big paperweight though. I personally think you'll have enough to worry about with all the upgrades you want to do. When you first fire up a rebuilt engine, you want to know the rest of the installation (fuel system, wiring looms, ECU etc) work properly - otherwise you're never going to know whether any issues are the engine or the installation. If you buy a running engine then as a minimum it can be used as a known runner to get the rest of the car working around it, before progressing with the rest of the power increase.
Personally I like to do things in stages. If something doesn't work you can undo the last thing you did and work out what's wrong. I think a lot of people can find themselves at a dead end by doing the whole lot of different, new and unknown changes in one go and then have no clue where to start looking when it doesn't work. Most new things don't work first time. Successful projects are all about breaking things down into bite sized chunks which you can start and complete as you go. Unless you've done this upgrade a few times already, you'll be up to your neck in loose ends before you know it
My advice:
1) Get a Zetec, but if you won't do that, choose which V6 you want to use.
2) Get that engine running in the car as it is. You've plenty of electrical & plumbing to do, so it's not a waste of time offering the new engine up then removing it again - you don't rip everything back out. The new looms and ECU stay with the car, only you
know they work, before you start interfering with the engine.
3) Remove engine, fit your new exhaust headers and either supercharger or turbosuperchargers, intercooler and pipework, the reinstall engine with new clutch. Install any drivetrain upgrades you want at this time.
4) Test it, thoroughly. Clock up a few thousand miles on it and get the "shake down" period over. Establish what mechanical or electrical gremlins you've introduced and resolve them.
5) Do the bodywork that you want done.
If you must have some half wit fit one of those god-awful aftermarket alarms using Scotch-blok on the wiring looms to wake up the neighbours with a false alarm once a fortnight, whilst introducing new and undesirable electrical 'features' then get that done at Step 1. You really don't need some muppet hacking up your ignition and immobiliser wiring while you're trying to get a new installation working. I have a rather dim view of 'professionals' who fit alarms. I've only seen 4 of them and they were all horrific abominations. I'm sure there's someone on the planet who can do it properly, but until someone points him out to me I'll run away screaming at the sight of a car with an aftermarket alarm. Actually, I'm that retentative that it drives me mad if the OE keyfob doesn't work!
