Hi Matt,
Yes, it was all pretty straight, and if I did miss anything the combination of gasket and the blue RTV should take care of any irregularities…
I bloody forgot to put the gasket in first time… just the RTV between pump and plate. So after I removed the pump, inserted the gasket and cleaned all of the excess ‘squeezage’ my hands are blue like i’ve been doing something inappropriate to a Smurf!! 
I’ve just started the engine in my Austin 7 Special. After a few adjustments it just fired up, such a good feeling. 22 years since it last fired in anger. It may be a pain getting there but well worth it.
Make sure you’ve got the corerct timing cover gasket fitted. Later (XJ6 patter) will allow water into the oil
You could remove the cam covers and stick the boroscope down into the front cover and see if there are any dribbles.
Thanks Andrew, I wasn’t aware of that. I think the block wass from a Mk10, the head is XK150 and the front cover … can’t remember…maybe I have a compatibility issue.
Looking at my zoomed in photo again and noticed something which needed to be zoomed on even more - looks like it definitely does need that RTV for low areas and gaps. See blue lines this time.
Day 2…
After tightening the water pump into place last night and giving it overnight to cure, I reinstalled all hoses and the radiator and refilled with water.
Unfortunately the same thing is happening. Water level dropped in radiator and came out of sump.
I have removed the front breather cover and the exhaust rocker cover but I could not get the boroscope down past the chain assembly to see anything.
I could not hear gurgling or anything like that, and the flow is just a trickle from the sump.
Next step is to remove the front chain cover and see what I see.
FYI Block prefix is ZA, which should be a 3.8 Mk10
Head is VS prefix so XK150.
As far as I know these should be compatible.
Prior to doing any further mechanical work…and from afar 
In theory, at this point, I would apply air at about 15 psi, which I would probably just clamp an inner tube over the radiator neck
Am I wrong this will push coolant and air, and you should hear hissing ?..see bubbles if its external ?
In theory, I cannot see any harm could be caused (unless too high PSI used)
does sound like a parts mismatch somewhere
going to garage to try this now…
Thanks Tony, but I cant identify the location
I couldnt hear any water/bubbles/air (although I did find a heater hose-clamp I didn’t tighten enough!)
It definitely worked in pushing more water through the breach as the flow from the sump-plug increased.
I think I’m just going to bite the bullet and take the timing cover off. I’ll order some gaskets first, and give it some more thought whilst waiting for them.
On an XK it isn’t too difficult to remove the oil pan, so I think it would be informative to take it off, fill the system with water and see where the water is getting into the crankcase. If it is at the rear of the engine, for example, there is no point in exploring behind the timing cover.
Take off the sump first. You have to undo the front sump bolts anyway and my sump had locating pins from memory going into the chain cover. You can also give it a good dry out, water may have gotten into your oil pump
Ok, already, already! I’ll take the sump off!!! 
Stay tuned…
Since you have parts from different engines, did you mill the block with the timing chain cover on?
Hi Bob,
Yes I did. I had them decked together.
Any news? 10 characters needed
Too busy at work, so I have to wait for the weekend before picking up a spanner… I have to pay for this hobby somehow…
Well thanks to everyone who suggested sump-off.
and here is a video of the leak in all it’s glory… Leaking water
I didn’t want to take the sump off, as I had spend time carefully seating and sealing the sump gaskets etc when the engine was on the stand to try and avoid leaks. I see now it is the only way to be sure of where it is originating from.
The cover’s seal with the block for the water channel (pump discharge) seems good and I can’t see water out of it…
Maybe I stuffed up the sealing of the intermediate timing gear shaft, Maybe it’s a crack in the cover that I somehow missed…
Lets remove the cover and find out!
Neither - horrible red gasket goop that never seems to cure -
I think I may have it *(although I said that last time…)
Rear of cover shows a water trail from one of the studs.
The cover was repaired by the machine shop as I had snapped the original stud off. They tapped and drilled it. There is also evidence of an alloy repair done for this,
The studs I used for this are too short on the UNC thread end, and dont fill the hole… You can see how much unused thread there is on the back of the cover photo…
A good long stud (hee hee) that uses all of the thread, and treated with sealant as it is installed should fix this… ( I hope)
