Will straight pipes hurt my valves?

Same here but with a C15 mbn. With windows up nothing still though.

 

^The N-14 powered W9 with straights I sometimes drive is the same way too. Its turbo whistle is what hurts your ears if the windows are down.

 

Straight pipes won't hurt the engine at all. The engine will breath like never before and the engine will seem more responsive because of the free flowing exhaust. The turbo is all that's needed to keep enough back pressure to keep the valves from warping, then you have maybe 15 to 20 foot of exhaust piping that cool air has to travel through as well. It's like I just read and agree with from another post, as long as the exhaust temp before the turbo is 350 degree or below the valves and turbo bearings live long happy lives and are in no damage of warping the valves.

 

It's a sweet truck most euro trucks are .
Smaller cab but better and safer , unless of course you slam into a tall concrete wall.