Could a bad exhaust hurt the engine?

[Zack1978]

Hey everyone,
As noted below in another thread, I think the head gasket is bad on my 79 4x4 p/u. However a while ago, the exhaust broke at the muffler, so it is just the pipe off the manifold. I have not driven it that much with the broken exhaust but a decent amount. So could I have f'd something up in the head because of the broken exhaust? I never knew that a bad exhaust could hurt an engine. I hope in fact that it is just the head gasket. Any ideas?

Thank you,
Zack

[Zack1978]

Here is the link to the other thread:

http://www.wildyoats.com/vbulletin/showthread.php?t=10950


Zack

[syncrogt1]

My understanding is that you can only damage the motor by having an exhaust leak very close to the exhaust port (manifold/head surface). At idle or decel, this allows colder air to hit the back of the ehaust valve and the rapid heat cycling will cause it to crack and lose compression(called a burned valve). This typically only happens when your exhaust manifold gasket is damage where the manifold meets the cylinder head. If some where downstream of the manifold there is exhaust problems which decrease backpressure, your engine will suffer driveability problems. It may rev quicker but torque may drop. I don't see how this could cause a HG problem though.

[fourwd1]

An open exhaust eliminates backpressure, which I think can cause burnt exhaust valves over time.