Will straight pipes hurt my valves?

The engine will be fine. They might hurt your hearing though. I'd recommend a small resonator /muffler be installed.

 

Put high flows on it, if it's a standard muffler, you can get them from Ryder parts and other places for around $100 a muffler, your truck will run better and it won't be too loud.

(Search other mufflers threads for details.)

 

Won't hurt a thing. I've ran straights on every truck I've driven and driven them hard.

 

I too run straights on all of them no resonator or muffler. Cats as a rule are not loud at all with straights, unless they are barely above the cab. I run 6 inch BTW and have run 8 inch they were really quiet as well compared to others.

 

Free flowing exhaust helps your engine. I have heard that it may be bad for Variable geometry turbos. (they may overspeed) Bigger is better 8" will sound mellow on a cat. I would put some kind of muffler in the system (Grand rock QP inserts are nice) Also Pennsylvania likes to bust guys for no heat shields.

 

That's what they said about short headers on gasoline engines. When you shut it down the cold air will enter the short pipes and warp the hot exhaust valves. I ran open headers on an old odd fire Buick V-6 in my old Kaiser Jeep CJ and it never hurt anything except it annoyed the neighbors.

 

You won't hurt the engine. What you could do so you won't need a hearing aid too soon is buy a muffler from pittsburg power and increase your mpg....