Posted by Troy Rudolph on December 13, 2001 at 15:05:47:
In Reply to: learning about engines, 101, 3.5liter vs 2.8liter posted by Adam Wilson on December 13, 2001 at 13:25:27:
The external dimensions of the block are the same across all M30 engines - or, they wouldn't be M30 engines. What differs is the bore and stroke.
displacement----------bore-x-stroke
2.5L..................86mm x 71mm
2.8L..................86mm x 80mm
3.0L..................89mm x 80mm
3.2L..................89mm x 86mm
3.5L(3430cc)..........92mm x 86mm
3.5L(3453cc)..........93.4mm x 84mm
The center-to-center bore spacing is the same across all the engines because the blocks are the same design. Clearly though the engines that have larger bores have less space between the walls of adjacent cylinders. In fact, the 3453cc engines have no space between the walls of adjacent cylinders. The bore walls are "siamesed" meaning that there is contiguous metal between them. This means the coolant cannot pass between cylinders which is one reason that the early Euro 3.5L engines were sensitive to overheating problems IMHO.