Hy redsshed37, an old Wayne high performance chart lists the max overbore for a 228 and 236 engine as 3 15/16", but it cautions that sleeves may be requred to achieve that. You are talking about an overbore of at least 0.15625, and thats just to standard bore pistons [248]. Most machine shops can sonically check a block for cylinder wall thickness these days. The two engines 228 and 248 both use the same height block 11 1/4", hope that helps.
