L-block B230s were put in '93 240s, as well as the other Volvos 700s and 900s with the 4-cyl. red-blocks.
1) As RHAIRE stated, it's got oil squirters to better cool the pistons;
2) it also has a different set of timing belt gears to go with a different timing belt (you can't use pre-'93 belts on this engine), and things like IPD's adjustable timing belt gear can't be installed on this engine -- reason is, the "teeth" on the underside of this revised timing belt are round, instead of rectangular as on the pre-'93 belts, and the gears' teeth for them have to also be rounded. The reason for the changed belt is that Volvo supposedly hoped that this new belt would have a longer lifespan (i.e., it would have a 100K vs. the conventional 50K mile replacement interval) but it didn't pan out -- you still have to change it at the same interval.
3) I am told that the L engines have different bearings to further minimize wear -- can't testify to this, though.

You can easily tell the B230-L engines, as the engine number's label on the top half of the timing belt cover says "...-L" after the engine's number.