Thats right DD I couldnt understand this myself
on Ozdat.com till I did the weighing at home.
Its been explained to me by a genius in L series
engines who`s building the most radical L20b Ive
ever could imagine with inlet valves that change
angles to be more central during full lift in order
to avoid the sides of the bores and make the inlet
charge more centered away from the walls. Unlike the
A series which has valve pockets at the top of bores.
Well he explained that the L18 was to be used for a
diesel version with bigger bores & was cast thicker
round the bores in some cases making them siamesed for extra strength. These blocks later labelled L18W.
L16 max bore is 86 before wall flex causes blow-by
where some rare L18s can go to 90mm!!!

If anyone wants a very rare L18 x-rayed block from a
Laurel confirmed to take 90mm bores pls PM me for owners
details as he has only 2 over 40 years building them.