I am curious if it is bad to run without exhaust. I only have the headers but nothing after that. I was told but someone that if I leave it like that, it will burn the valves and cause a lot of damage. Can anyone tell me if this is true?

 

I wouldn't run without exhaust unless it is a few miles down the road to the exhaust shop. Not only will your car be LOUD without pipes or mufflers, it will also be illegal.

When I started my car to break in the engine I made make shift exhaust out of the flex tube from the auto parts store. After that I had my car towed 5 miles down the road to the exhaust shop.

If you run without exhaust you run the risk of the hot exhaust gases damaging plastic components in your engine bay. You will also get exhaust gas in your face.

 

if you have headers on it you will be fine but loud. the issue with burning a valve has to do with leaks near the cylinder head. when you decelerate the engine will pull some of the exhaust gases back in from the exhaust. if there is a leak close to the head it will pull in air (oxygen) which will REALLY heat the valve and over time can damage it. with headers the tube is long enough that all that gets pulled in is burnt exhaust gases.