Ugh, This thing has been plagued by bad luck lol. Took out the supercharged/e85 340 for a ride to work on tuning and trouble shoot a few ignition problems. I let it warm up for maybe 5 minutes, checked trans fluid and began taking it around the block when I realized it was creeping up to 220degrees. I was just turning onto a main road so I figured I'd give it some speed and let the air cool it but it started climbing slowly. I turned around to head home and just as I started pulling down my street the temp started climbing quickly to 240. by the time I shut it down I was at around 250 and coasted it into my driveway. No engine noise, but I had some water spraying out of my hose clamps and the radiator was making a A few loud bangs after I shut down.

Turns out the brand new thermostat I had in there stuck itself closed.

I'm just really worried about the motor being it is brand new, only has maybe 50 miles on it and I'm still running break in oil. I mean it only ran at 240/50 for a few seconds at most, should I be worried? I wish I could have shut it down sooner but the street was busy with traffic coming up behind me and I didn't feel safe getting stuck on the main road when my driveway was just a few yards ahead.

I've had stuff that hot before and it never hurt it. Scares ya a lil tho. My overheating adventures happened with stock stuff.

My 408 over heated a couple times. Didnt hurt it. Forgot to turn the water pump on. Needle on autometer temp gauge was pointing straight down where there were no numbers. Couple yrs later i found the valves were stretching. Not sure the heat hurt them because there was 8yrs run time on them.

No big deal. Most likely didn't hurt anything. In 2009 I was racing at the Mopar Nationals in Columbus. Blew the fan belt during my burn out. No fan, water pump, P/S. Made the pass anyway. Pinned a 250 temp gauge on the return road. No engine damage. Car ran a tenth faster on that pass than it ever ran before.

You should be fine, I forgot to plug my water pump back in once and didn't realize until I was sitting first in line in the left hand turn lane at the busiest intersection in town. It was off the temp gauge by the time my light turned green and I was able to pull over and plug it in. I was more worried about cooling it down to fast than I was the actual temp. No issues and it lived on for several more years before I pulled it for another engine.

The temperature you saw on the gauge is not the highest temperature in the engine, which was probably in the spark plug and exhaust seat cooling loops. At those locations your safety is the cap pressure which prevents local boiling.

I had the same thing as him on my old M.W. stocker at the 1988 NHRA World finals
I had let a friend drive it and he didn't see the temps climbing on the return road, I got into the car at the turn out into the pits and saw it, had him shut the car off and we found the fuse to the electric water pump had blown, fixed it and let the motor cool down and then drove it back to the pits, that STUPID car pick up a tenth on the next run
OP, if it will help you figure out if you hurt it or not do a compression check and or leak down test and look at all eight spark plugs, if it looks go good drive it somemore

I wouldn't worry about it at all. I've had em that hot before w/ no problems.

I used to take new builds out and run (beat)them hot on purpose then re torqued the heads, checked the lash and called it good.

Some dont understand you can break in a new cam by driving it.

If they made it through the first 30 minutes of abuse I know id not have to worry down the line.

I do it a bit different now.