Since the information is not easily found, here's a great little guide for you all installing a Prestone flush kit in your LS1/LS2 engine:

A = Water pump outlet to heater core, 5/8".

B = Water pump inlet from heater core, 3/4". <-- hose where the tee goes, in the straightest area you can use!

C = Water pump inlet / thermostat housing (in to engine from radiator), 1-1/2".

N = Water pump outlet (out to radiator, from engine), 1-1/4".



My install:


Clearly Prestone's guidance SUCKS! “Hose #2 runs from fire wall to top of engine. This is the heater inlet hose.” :bang:
| Prestone®