1.8 Carb engine rebuild - pointers needed!

Hello, as some of you may remeber i bought my GX last year, at the time it was fitted with a 1.8 carb engine. This had lots of power, and was fantastic on the motorway(as it proved when the chap with the new passat tried racing me on the M6!).
Anyway, long story short, it was knackered and got replaced with a 1.5 JB code engine which was original fit for the GX.
This is a good engine, but as the GX is used more for weekend and occasional daily use and really i want more power, and the tired 1.8 at the back of my garage is crying out to be looked at,
I know the head has warped due to it overheating all the time, and when i stripped it i noticed piston no.4 had a scratch,
Basically what i need to is where do i go from here?
I want to do a full rebuild on it, and ideally i want to do as much of the work myself, could the scratch be removed from the block casing, will i need any special tools, if so what? and where is a good spot to by engine parts, any information will be great as this is my first engine rebuild.
(Incidentally i will be stripping the head completely so may look into gas flowing it while i'm there, any pointers on this will be good too), sorry for the essay!
Thanks, Tom :wink:

Where is the scratch? Inside the bore?

Yeah the scratch is inside the bore, i think it would polish out though, also theres a bit of corrosion to the waterways, what can i do about that?

Is the scratch above or below the piston line? Waterways need to be buffed back and replaced with liquid metal

It depends how deep the scratch is, re-honing the cylinders might/might not remove it. If not, then you're into a slight oversize rebore and new oversize pistons, etc. TBH corrosion on the water channel is going to be difficult to address properly.

Normally what I'd do is use a typical ?100 secondhand engine as a starting point, remove the head and check the bores for no damage and around the castings, flanges, waterways etc for damage. If all okay, then skim the head, lap the valves in and use new valve stem seals and its not too far off good as new. The bottom ends normally last really well, 250-300k miles.

So given the ?100 cost of a different secondhand engine vs the cost of possibly reboring + new pistons, it might be more economical to go down that route.

i would say the scratch is below the piston line, but i'm not sure what that means? How would i go about removing the corrosion? dremel etc? The corrosion is'nt to bad, it just bugs me, and i would have to remove as much as possible.
Like i sadi in the first post paul, it was a good strong engine, the head was warped was all which meant it pressurised itself and chucked its coolant back out, never leaked oil etc. I would like to re use, would the next step be strip it fully and check scratch and components?

By below the piston line I mean is it below the travel of the top ring ie below the max depth the top ring can travel down to. If it is then it can be filled and re-ground back. Yes a dremel will do fine, also you want a good quality liquid metal something like 75% metal in the mix, an engineering shop should be able to assist by supplying. This stuff can be ground, drilled and even hammered when set so no issues using it in waterways.
If it was only a cooked head why are you going to the bother of stripping the bottom end down, it is due to the scratch? If you run your finger nail through it does it catch?

Nope its as smooth as a babbys bum! checked today, its just visible is all, so i want to sort it. Onl;y want to rebuild so i can be 100% about it, don't want to rebuild the head and then find the bottom end is tired especially as i want to gas flow the head, but thats my only reason.
So liquid metal i want, any idea how much it costs? Cheers for the advice so far by the way.

me and a pal of mine are currently rebuilding a 1.5 lump. The way we have tackled it is to strip the block take all the bits to an engine builders get them to measure everything order new shell bearings, piston rings etc. (got them to run it through there cleaner too).

Then when we get it back we'll paint it and put it back together. just make sure when you strip it down you mark up everything where it came off e.g no.1 cylinder and paint an arrow on in the same direction on every part. when you put it back together put everything back in exactly the same place.

the engine builders will be able to tell you if the cylinder wall needs any work if it does i'd let them do it if it's your first rebuild.

hope that helps dude.

Yeah cheers, just need to shift all the stuff in my garage then maybe i can make a start on it!