Is there a difference between the ITR, GSR, or SIR crank? I heard that the ITR crank comes very balanced from the factory already and if this is true, this would make it the best out of the 3. But what about the GSR and SIR crank? Which one is better?

 

SIR crank has a shorter stroke, hence 1.6 liters w/ same 81mm bore. As for balancing, any crank is balanceable even after factory balancing. The cranks are not interchangeable between the blocks, so purchase a block w/ the displacement that you want and go from there.

 

True that the B16 is different from the GSR/ITR. But only in stroke.

They (DOHC VTEC cranks) are interchangable.

For instance, the ITR and GSR are completely interchangeable. The B16 will fit in the GSR/ITR block, but you'd be de-stroking it to get a better rod ratio.

Essentially, the B16B (CTR engine) uses the B16 crank with special length rods in a GSR/ITR block to achieve it's almost perfect rod ratio.

HTH