Am currently in the process of renovating my4.2L series 1. Have had the engine out for a couple of months while I tidy the engine bay. Yesterday I opened the engine up and was delighted at the condition.
Punched all the engine core plugs out - surprised to find that none showed any sign of corrosion - but I have a nice brass set ready to go in.
Cleaned out the core by blasting water through every available hole - a river of mud flowed down the driveway. (this may be related to the time I was at a remote lookout and blew a radiator hose off. After re-fitting the hose the only water available was muddy rainwater from a nearby puddle - I put this in and ran another 200miles home)
Cylinder head was next to come off. Strangely I could not at first turn the cam chain tensioner with a pair of long nose pliers (have done it this way before) I had to make up a two pronged tool to get some purchase and it turned - I think the adjuster had become dry of oil in the long time the car was off road.
Cylinder head separated easily but did not want to lift. I used a succession of aluminium wedges to slowly lift until I could get a good sized piece of timber under the middle to lift.
Results - all studs in excellent condition, so no need to replace, and no cracking of the bore between any cylinders evident.

I must have got a good one!

 

Here is a shot of the core plug holes - studs are excellent

 

What is the condition of the cylinder bores?

Is the cylinder head also in good condition as that is the area most XK engines suffer failures?

 

Cylinder bores look fine, if a little smooth - no honing marks visible. Engine had good compression prior to removal.

Yet to dismantle the cylinder head, but it was my impression that blocks were of more concern with this model, I don't know of any cylinder head issues unless you let it run out of coolant.

 

We were going great until we broke off a corroded stud putting the rebuilt head back on. Engine seemed very like yours minus the mud. Opening a whole new can of worms.
Twenty minutes later I had sourced a short motor from Peninsula Jag. Cheaper than we would have spent on parts and machining the block etc. Had the deal done next day.
Two years down the track, couldn't be happier with the engine. Maybe try using a piece of pipe over the studs to tension them before refitting the head so you don't get caught out like we did and waste a head gasket in the process.

 

Thanks for the tip Clarke. I think I will do this. I tried removing a couple of studs using the double nut technique, but they slipped and the stud would not turn.
I think I'll use a short length of pipe as you suggest and tighten to the finishing torque +10%.

And I now know that if all turns to s#*t, I can always use the block as a wine bottle holder!

 

Placed the head back on the block today. All the exhaust valves were replaced due to a lip that had formed on all of them about 3/4" from the top of the stem. Is this common with the XK engine? Clearly the valves once in do not rotate. Lapped in all the valves, managed finally to extract all the studs and everyone was excellent. Put back in with a good dollop of never-seize on the threads. I love the brass core plugs. Buckets and cams yet to go in.

First picture shows a replaced exhaust valve and my special tool for valve removal and fitting.