Sleeving is a way of saving a block, I don't feel it has any effect on rigitity one way or the other. The material in a sleeve probable is a more consistance throughout than a cast iron block, i.e. less likely to have hard spots. I wouldn't use sleeving as a means of encreasing a bore larger than can be done safely in the block. More heat in the combustion chamber? It would take a lab to measure any encrease, there will be a small heat barrier at the sleve/block interface, but nothing to worry about.Besides, practicle none of the sleeve is exposed to combustion, by the time the piston has uncovered the sleeve combustion has already taking place. The combustion temp and pressure will be highest while the piston is near the top of the stroke and they will decrease as the piston fallls in the cylindar. I've had numerous blocks sleeved over the years and never had any problems. One Cortina 1300 engine I built turned 10K with sleeves in all holes. Hope this helps. Bob
