"<<" and "+" should be faster than "*" and the old formula should be better parallelizable than the new one:

j << 8 , k << 16
i + (j<<8))
k + (k<<16)

minimum of 3 cycles vs.

i * 37
(i*37) + j
((i*37) + j) * 37
(((i*37) + j) * 37) + k

minimum of 4 cycles

so I dont think thats a speed up.