I intend to replace my 1600 xflow with a 2.0 Zetec. Which gearbox will a Zetec fit? Do I need the wiring loom from the donor vehicle? Can I use a Weber 38 dgas or twin 40's? The engine is likely to be post 92 so how do I stand re a CAT? Are there any other wiring issues I need to know about?

Check this blog post. It's st170 but virtually the same thing.

http://forum.wscc.co.uk/forum/index.php/blog/19/entry-29-engine-swap-xflow-to-st170-and-4-speed-to-5-speed-box/

As for a cat, afaik the emissions remain as per original engine, but could be wrong!

[Edited on 28/5/15 by kingster996]

if you are swapping the engine no problem as your car is registered without a cat, yes you can fit twin 40's or 45's. Any rear wheel drive ford gearbox fits as they have the same bolt pattern ideally a 5 speed box from a capri or sierra. There are mods needed to the sump you need something to give a spark megajolt is a cheap option you can however use the ford ecu Big Wasa is you man I believe for the info on that part. If you decide to go the webber route give me a shout I have a pair on a zetec manifold

Does all that mean that I can bolt a 2.0 (or 1.8) Zetec straight onto a Type 9 gearbox, fit an appropriate exhaust and twin 40 Webers without the need to get involved with the original vehicles ECU and wiring loom? I appreciate that I need something to make the sparks work like a Spark Megajolt and mod the sump.

I replaced a x-flow with a 2 litre Zetec back in 2001.

The Zetec bolted strait onto the type 9 box. All that was required was a spigot bearing knocking into the end of the Zetec crank.

The existing Weber 45's fitted strait on but I needed a suitable Weber to Zetec inlet manifold.

I used a Weber Alpha ECU. It was easy to fit and came complete with a plug and play wiring loom and a pre installed map that actually works. There are cheaper solutions out there but as a colour blind electrical numpty I needed a simple solution.

I used a cut and shut Dunnell sump. Scholar engineering make an identical one for less money (as I found out later). Again, there are cheaper solutions (i.e. DIY) but IMHO skimping on engine lubrication is just plain stupid.

The engine mounts were bought from a reputable source.

I used the existing exhaust but had new downpipes made.

I used a special steel flywheel on mine since the Zetec 2 litre one is a boat anchor. The 1.8 one is a direct fit and much lighter and is best budget solution. Lightening standard flywheels should never be done IMHO. Even "experts" can get it wrong and if a flywheel lets go at 6000 rpm (or more) there is lots of metal flying around near your legs and feet, never seen replacements advertised. A 2 litre DOHC Sierra clutch was cheap and bolted strait on and is still there 14 years later.

I reused the x-flow starter (direct fit) and alternator (modified the bracket) with a new suitable belt,

The original Ford stat housing was retained and lots of hoses were needed to plumb it in. If its a Silvertop you will need an Escort Zetec waterpump, if its a Blacktop you will need to fabricate or buy a suitable idler to reverse the direction.

If you have a mechanical fuel pump on the x-flow you will need to fit a suitable electric one and a regulator.

If your car was registered without a cat you will not need to fit one.

On a used engine always replace the cam belt and pulleys.

Once running a quick visit to a Rolling Road to set up the mixture and away we went.

Thanks very much for the very comprehensive reply. Best go and find a Zetec engine!!