All the "L" series engines were prefixed with an "L" They were found in both 4 & 6 cylinder form & all are single overhead cam engines with a chain drive to the cam.

The smallest one that i know of was the L14, but i have a funny idea there might have been an L13. The odd one out is the L20b, which is a 4 cylinder. It became necessary to use the "b" suffix as there was already an L20, which is a 6 cylinder. The number is the engine dicplacement in Litres. By placing a decimal point after the first digit, it becomes obvious.

The L16 was used here in the popular Stanza range & in the classic & VERY popular Datsun 1600, otherwise widely known as the model 510.
"A" series of engines are the smaller, overhead valve engines that were made in capacities from a nominal 1000cc up to 1500cc Both series are GOOD engines.
Chris
The two of them bear no real resemblance beyond being 4 cylinder inline types.