What's the normal running temperature for a 455? mine seems to be running kind of hot. almost up to 200. i just had a tune up and a cooling system flush. Maybe a problem with my gauge? it's aftermarket. any help would be appreciated.

It's going to depend on what thermostat someone may have put in. If they used a 195 then you don't have any problem. My personal preferance is a 180 and the only reason you would have for it to be 200 would be inefficiency somewhere.

200 is a little hot for any motor to be running, you could start getting dieseling(run-on) and backfiring problems. It could also cause the fuel-air mixture to ignite prematurely causing knocking and even engine damage.
The optimum running temperature for most gas engines is 88* celcius, which is somewhere between 170-180* fahrenheit.

hope this helps
-Ben

It could be that your fan clutch is starting to let go. They tend to fail slowly so that you barely notice until they are totally inoperative. Here's a way to test it. Before you start the car next the next time, turn the radiator fan by hand to get a feel for the resistance. Run the car and get your 200 deg F temp reading. SHUT THE ENGINE OFF. Turn the fan by hand again. The difference in the resistance should be like night and day. If it isn't, bad fan clutch. You could also have a deteriorated water pump (as in vanes have dissolved thanks to not changing the coolant).

Thanks, I will check all of those things. However, I did just get a new water pump. also, I noticed that if the car gets up to 200, if I go back out and try to start her again maybe 5-10 minutes later, the starter hesitates a bit then kicks on. also, my mechanic said he advanced the distributor, would that change anything? I am running a hei on my 73 buick engine. he advanced it according to the 76 settings. cause he told me my distributor was out of a 76 455.

ok, this is weird. i got in my car today and drove it to school. It ran at an even 170 the whole way. then, when I was coming home, it got back up to 195. course it was 170 on the freeway and 195 in stop and go. so, does this still sound ok?

you are pushing more air through the radiator at speed than you do in stop and go traffic. perfectly normal.

If you are not getting detonation (aka pinging), not puking coolant after a hot run and letting the car sit for a while (condition called hot soak), not have a "dieseling/run-on" problem, I wouldn't worry about it. It sounds like your mechanic set the initial timing for fun driving. Buick engines are able to tolerate a lot of initial timing. If you are really worried about overheating, you could add an electric fan triggered by you or a thermostat. Like heidigirl mentioned, a separate cooling fan might give you that "freeway temparature" throughout your drive.