Just built a TMAXX and bought an OS TM for it. Before installing it into the truck, I noticed the carb does not close on it's own. I don't know that it should, just curious. I was able to get it to close via linkage and throttle return spring in the install, I was just wondering if it is OK that way.
Getting ready to break her in.

Your engine is normal.

No, it's not "normal"
It is awsome.
It is a little different, building a truck and installing and instaloling an engine into it, than simply replacing an existing powerplant. A few more tweeks to iron out this way.
All worked out well, but in the future, I would probably break-in the new engine in an existing, well working rig, just to make it smoother.
No regrets, however, it was fun, and learning about all this stuff is half the fun!
I have is working well, altho not tuned for peak, perhaps, but temps are running 200-230 if working it fairly hard.
Thankyou for the reply!