273 and 318 the same block?

grumpuscreature said

Nice idea but there is one fly in the ointment. Ma Mopar in her infinite wisdom used different water jacket cores in each block in her efforts to make each one as light as possible. The cylinder walls in each block does not have enough thickness to allow much more than .060" overbore. The one exception to this is the '71 360 blocks which were cast using 340 water jacket cores and can go out to 4.1" safely. Hope this helps...

Click to expand...

The 273 was the first LA engine and had many core shift problems because of the new design.

Quote from Allpar: The LA, introduced in 1964, had the same basic design but was very heavily modified. The lightweight ("L" A) or thin-wall casting and heads saved around 50 pounds; the wedge-shaped combustion chamber was much smaller than the A engines’ poly heads, greatly reducing the size and allowing the first LA engine (273 V8) to fit into the small Valiant.

Any overbore more than .030 and I would recommend the block be sonic checked. A thin cylinder wall could ruin more than your day. tmm