They probably tried to put a system for Renault 1.3 liter from a Dauphine (was that their little shitbox I test drove one time?) on the XJ. They lasted 1 year or 12,000 miles as designed.
Wouldn't a bored out engine transfer more heat to the coolant instead of running it out the exhaust?
Hard to say, that was my first thought, but heat transfer, conduction and convection, and wall thickness are all involved, and the calculations can be quite a nightmare. In this case even engineers use empirical data, as the numerical calculations (and assumptions) can be way off. My thought was the heat can transfer faster through a thinner wall, get out faster, thus reduce the internal engine peak temperatures further, faster, thus reducing the peak coolant temps leaving the engine, thus reduce the cooling system operating temps.
Look at this way (and correct me if you see flaws here), if I take a heat source and heat a plate up on one side, then I cool the other side, lets assume the heat source is the same BTU (but we know that the stroker is more efficient, can deliver more power per revolution, burning the same amount of fuel, so that assumption may be wrong, the BTU input to the cooling system may be lower), then we use a thick plate in one test and thin plate in the other, the thin plate will cool faster, and heat faster, so heat gets transfered to the cooling system faster, earlier, sooner thus the engine operates at a lower peak temperature.
The thick plate is slower to transfer heat, (think of radiators, do you want thick tubes or thin tubes in the radiator core?) so the engine gets hotter in order to reach equilibrium across the plate wall, so the engine runs hotter, thus eventually make the cooling system run hotter.
Now that I have written it down, I an not so sure my last statement holds water, but I think the rest is correct.
Of course if the engine runs hotter, then more cooling is done through the exhaust pipe, long story short, I don't know for sure, but I know enough to ask the question.
