What is an unsafe temp? When climbing a hill while towing I'll hit 210 or maybe just a tad over the 210 mark. I've heard that this is bad and causes premature head gasket failure? Is that true? Thermostats are set at 190 degrees so are the gaskets designed that precise that a 20 degrees variance will make a difference?

my lb-7 just blew head gasket. when it went the temp shot up to 230. when we pulled it apart both heads were within .001 dam near perfect. my truck was getting up to 210 on the interstate but come to find out it was a waterpump issue causing the problem. I would check everything real good. this has costed me a fortune. almost had the truck towed to the bank:banghead:

Thanks.. The waterpump was leaking about 20K miles ago so I had it replaced. Truck normally runs fine even while towing. It's just a couple of longer steep hills where she gets hotter. With a new motor going in soon I was thinking about replacing the water pump with a high output one from Heath but remembered just how much they cost. I asked the mechanic and he said not to worry about it. He would clean around the radiator to make sure that's all clear. I wanted to float the idea out here to get others opinions. Is 210 or 215 really bad for these motors?

Over 210 is not good for a 6.5. The factory temp gauges should start to go "into" the red at 210, because that's when you'll start to do damage. You can blow headgaskets, crack the heads and even crack the block if you get it too hot. Running a 6.5 is like playing Russian Roulette. It's not a matter of if, it's a matter of when.

An older chevy 350/305 gasser can run at 220'F just about forever and flirt with 240'F occasionally with no problem, why are the 6.2L & 6.5L engines so different?
On my 6.2L the red mark starts at 230'F and on my camaro it starts at 260'F.

My trucks "red zone" is 230*F. I have an aftermarket gauge on it as well and it usually runs 190*F. Hottest I ever saw was 200*F.

210 is the high side but when i was in iraq they were run at 230-250 zone in the red puch 14000 lbs down the road at 65 they took it for awhile we replaced a lot of 6.5 I went as far as punching the cat and muffler out and making a air scope for the intake to help keep them cool mine with the 24 ft stock trailer running 75 mph up hill it clime a littel over 210 but cools backs off on the down hill or flat ground

try a low temp thermostat. Diesels run much cooler than gas engines so they shouldn't see such high temps.