[sevisehda]

I run 3/4inch tubing in between my johnson pump and my rad. The only reason being the pumps outlet is 3/4 and I had to redo the barb on my heatercore anyway. After the rad I run 1/2in to my CPU than it is split between 2 parrallel 3/8 tubes.

The difference in resistance between 3/4in and 1/2in for most systems is minimal. If you can run 3/4in easily than by all means try it. However most likely the 3/4in will be to hard to do tight turns in most situations.