When Volvo decided to add piston cooling to the redblocks, the way they went about incorporating the squirters into the block casting was by a modification of the basic casting to add considerably more metal on the passenger side of the block to allow for a slight outboard movement of the main feed oil passage [from the oil pump to the oil filter boss] and a slight inboard movement of the main gallery oil passage. The outboard move of the main feed is apparent; the inboard movement of the main gallery line might be a personal mis-observation.

The four humps seen along the main gallery oil passage are there to provide substantial support for the machined bosses and the drilled/tapped mounting holes for the squirters themselves. Close examination of the block externally and internally gives the impression that the added metal was to minimize any possibility of passage porosity due to thinness that could result from casting variations. It could not be described as some kind of a bandaid add-on. It really is a hefty enhancement of the block.