Just flushed my cooling system and went driving,,, combo of highway and surface streets,,,,when I stoped a guy with a laser temp gauge hit the radiator cap and the temp was 212 degrees,,, outside temp yesterday was 104 at the time,,,question is what temp is to high?

200 ci 6 cylinder, 1 bbl carb, stock exhaust, 3 row radiator, 5 blade fan , 3 spd manual tranny, no fan shroud ( am working on that one right now)

 

you stopped and switched engine off or was it still running?
If you have a good quality coolant at the right proportions, and a working 13lb cap, boiling point is well above 212.
212 is on the high side, but so is 104!

 

Since it was 204 in Phoenix today, 212 for the radiator aint bad!!

But seriously, considering the outside temp, and the fact that you probably did at least some low speed / stop and go driving toward the end of the trip, I don't think 212 at the top of the radiator to be out of line at all. Remember, the hot water enters the top of the radiator and cools as it goes down.

 

That is pretty much normal. You have no worries if you have about a 50/50 coolant water mixture. You might want to dump in a bottle of wetter water when the engine is cool to help keep it down.
If you don't have a recovery tank, and the 13 pound cap isn't opening and spewing coolant on the road, then you are good to go.

 

On my dads vettes it only matters how traffic is going. On Friday we went down to San Diego and on the way was rush hour traffic. His Radiator hose blew off and knocked the oil cap off and then about a gallon of coolant went into his oil tank. HOORAY. that screwed him. He didn't drive it till he got the oil changed. However, it was about 250 when it blew, and going 65-70 on the freeway he was keeping it steady around 180.

 

much appreicate the know how but does anyone have an idea of a so called danger zone without frying the motor like a bad egg,,,temps here in Phoenix tomorrow is for 114 degrees, and the last time I fried a head ,,,( many years ago... thank the gods) the thing spun on the garage floor like a drunkin frizzbie and I'm sure the block probably felt the love also

 

As a rule, when the coolant is not boiling away, you are pretty much ok. Overheating is compounded by by steam replacing the coolant around the combustion chambers. Steam does not cool the engineat all. Keep your nose in the air, if you smell coolant beware!!

I would for sure have an overflow tank if I lived in Phoenix, or a similar hellish climate. If the engine boils over a little bit after you turn off the engine, this is not much of a concern.