If it gets hot while driving at highway speed it is not fans since they turn off at 35 MPH. Either the airflow over the radiator is insufficient or the coolant flow is insufficent. LS1s do not blow head gaskets from normal use, and if your coolant isn't foamy and oil isn't foamy then you probably don't have a head gasket issue. If the air flow over the radiator is clear and your air dam is in place check the water pump - take the cap off cold, leet it warm up to operating temperature and then when you crack the throttle you should see the coolant flow. If that is good, I would flush the system, replace the thermostat with a 180*, replace the coolant, and replace the radiator cap. Also check the radiator cap sealing surface, there was TSB on imperfections where the cap seals and the fix is to clean it up with 400 grit paper.
What mods do you have BTW?
Last edited by DaddySS; Jul 18, 2009 at 03:35 PM.