I'm sure its out there somewhere, I curious to know the difference between the LY5 5.3L and the L33 5.3L?

 

well, for starters, the LY5 is a GenIV engine - the L33 is a GenIII
the L33 is aluminum block instead of iron.
i don't remember the heads off the top of my head, but i do know the L33 has flat-top pistons for higher compression

 

Gen 3 versus Gen 4 as mentioned so knock sensors on the block versus the valley pan and a 58X reluctor on the timing cover versus the 24X at the back of the block.

L33 is aluminum block too. The LY5 has the same piston and head arrangement as the L33 did so nothing really there. The LY5 will have the TBSS style 87 mm intake as do all Gen IV 5.3's.

LY5 will be active fuel management however and of course the Gen 3's were never burdened with this problem, lol.

 

Thanks guys. Is the LY5 flex fuel compatible? Or, how can you tell if a truck is flex fuel compatible or not?

 

The LY5 is not flex fuel compatible. The injectors are smaller on the non flex fuel versus a flex fuel ( like the LMG) as example. I don't know the exact numbers so correct me if I am wrong but the flex fuel are around 36#'s stock and the non flex fuel ( LY5) are about 26 #'s.