So, after figuring out that my electric fan was not turning on, the heat issue is gone... I THINK lol.

My car basically hits 180, sits there for a while, then goes to 190, then to 200... maybe 205 and then back to 200ish.

Is that about right?

(engine is that weird configuration, 1971 455, 1968 428 H.O. heads)

My 400 runs at about 200-210 at highway speeds and 195 in the city.

You're absolutely fine at 205.

Probably no reason why you couldn't stay at the thermostat temperature. Check the impellar clearances inside the water pump.

http://forums.performanceyears.com/forums/showthread.php?t=411256

The 68 400 I rebuilt was hot running before I reduced the impellar/divider plate clearance from about 1/4" to 1/16". It's not on the road yet, but it stays at 180 whether at fast idle or curb idle. I even blocked the radiator to let the temp get to 220. It went right back down to 180 after I removed the blockage. So far, so good.

You're good at 205.

Pontiac's used 195* stats, and normal temps where 210-215.
Some 220.

And I think the temp light didn't come on till around 243'ish.

Mine never goes past 3/4's of the factory gauge - whatever that is.

And that's without the factory baffles (upper or lower) or the bumper mastics installed.

I LOVE my aluminum radiator.

Thanks guys! Yes, I have a nice high capacity aluminum radiator as well :P I think it helps.

My 67 bird's 400 would rocket to 210ish with the stock radiator. The new be cool unit was like a blessing to my piece of mind. With baffles,clutch fan,shroud installed correctly it hasn't went above 200.

in about what time? and running freeway? or traffic? at what speeds? outside temps?

205 is fine.....but you didnt tell under which conditions...
it may vary , if going 80 and then to a traffic light ,or slow traffic for awhile after ran for 30 minutes...even up to 220 at that would be ok, then down to 205 driving again....assuming hot weather too...
205 in cold weather may not be too good.

I would just add that mine is overheated at 225-230. I've seen some say that 220 is still ok. Well, NOT ok on my car. I threw the belts off the other day on my way home so the WP stopped turning and in the amount of time it took to wait through 2 stoplights I was already hitting 220. 225-230 by the time I pulled in the driveway. Shut it down and it was puking all over the place. Just saying.

interesting...when I bought mine it ran 225-230 all the way from Dallas to Houston, (250 miles), uphills 235 creeping towards 240, the idiot lights were set at 240-245 to come on...

and I`m sure you know to not fill up within 2 inches of the filler neck.

sounds like something happened to yours

Well something did happen as far as getting too hot. But it has always been the same way. 225-230 and it's over the top. And before everyone says my gauges must be off, I have two: the original electric and a mechanical thermometer in the crossover. They read the same.

hmmm,sounds like something happened...something blocking flow? timing?...
but to the original topic, I think we need to hear more abouthis 'overheating'...like under what conditions...driving or idle, driving how far , how fast ,slow down, outside temps ,etc ,etc

I was having this very issue, i have a 400, cam , headers and a 3 core aluminium radiator with a 1200 cfm electric puller fan . my car runs at around gauge indicates 210 220 degrees. I did the devider plate to impeller. with a 185 thermostat, with my laser temp reader , i have 190 or so at the thermostat.