I’m in the process of servicing the cooling system of my XJ.
Engine was swapped a long time ago by previous owner and it was coming of a Serie 1 XJ.
On the intake side, there is some serious carbon buildup on the valves.
I know PO was pretty old and driving the car “gently”, but are the XK engines prone to buildup carbon?
What do you recommend for cleaning without removing the head?
Thanks for your help, I’m not familiar with these engines.
Newer cars with direct injection suffer from carbon build up on the inlet valves, they are cleaned by walnut shell blasting, there are YT vid on the process.
And yes because the engine blow by gasses are fed back into the inlet the valves can get carboned up.
I guess the decarbonizing gasket set wasn’t named for no reason, i‘d be inclined to remove the head and clean everything on the bench instead of walnut shells, but that’s me, and if you can’t do it yourself it sounds like the best way to do it.
You can try Seafoam (google): it worked very well in my Cooper S. I note you must use it in a very well ventilated area (smoke makes it incredibly messy).
Removing the head will be the next winter project I’ll tackle.
I wasn’t aware of the decarbonizing gasket but yes, it’s pretty much self explanatory.
I’ll try that first and see how it cleans intake runners and valve.
I’ve never tried it yet but thanks for the advice. I hope my neighbors won’t call fire department 
I recently performed an Italian tune up on a vehicle that was doing many shorts runs, began pinging, (which was not fully cured by new spark plugs)
I did a few 1hr drives using maximum throttle on uphills, and keeping the engine near peak torque with gears. The pinging is now gone
The premise is excess carbon will be burned off
Care should be taken that the engine systems are up to such treatment though