Anyone know whats involved in building a good stroker out of a L20b blocked motor? I'm told to use a 240k crank, is that right.

Its not a 240k crank (240k is a six cylinder engine), I believe you need an L20 block and a crank from a z22 (from nissan navara.. not sure what year model). not sure what conrods or pistons you'd use, best to speak to some 1600 guys, its a fairly common combo

firstly 240ks are l series but with 6 cylinders so that will not work however read this thread

l20 stroker thread

Ozdat has about every possibility for L20 stroker motors in their forum . Tons of good info there.

They also have an awesome engine design utility just in case you haven't seen it.
Clicky

But here's a big list to get you started
clicky

use itheir a z24 or z22 as the blocks are prity much about the same but have fun finding a z22 crank there werth heaps know

im doing the lseries stroker at the moment with the z24 crank

Awesome! Thanks heaps.