While the cylinder head is totally dismantled, introducing an external oil drain from the head towards the block can be a smart go. Cylinder head porting can also give huge stream improves.However, The 2 are pretty comparable, and the RB25 is admittedly no slouch. You can visualize the RB25 vs the RB26 as much like the 1JZ vs 2JZ debate. The RB25/1