Ah right..
Well, doesnt really need a massive essay as its simple enough so il do a few lines whilst i wait for this kettle.

The cooling system is actually designed to transfer heat away from the combustion process when we get the burn to produce the most pressure at around 20 crank degrees after TDC.

If we retard so peak power is past this point, we start to drop out of the water jacket andf lose a lot of the thermal condution properties designed into the combustion area. Due to this, the exhaust gas leaves the exhuast valve, somewhat hotter than it may ideally have done.

that was reason 1:

Reason 2 is it hasnt had as long to cool down as it would if we had set light to it earlier

That help?