i didn't/don't. some say you do, i haven't and i've had mine off a few times. no leaks. just make sure they're good and tight

 

You can get away with reusing an old head gasket, just check it's condition and make sure it's not in too rough shape.

The gaskets are designed to be crush gaskets though and are meant for single use. Personally, I replace mine each time I take the headers off. For the minimal cost of the gasket you can avoid the cost of dealing with any problems caused if the reused gasket leaks, let alone the work involved in taking the headers off again to change the gasket for a new one if it leaks.

 

Depends which gasket you're talking about.

The valve cover gasket (the one at the VERY top of the engine) is generally reused many many times before it needs to be swapped out. Just clean the edges of the bonding surfaces and make sure there's no oil, debris before you put it back on. It's recommended to add some bonding agent/silicone on those U shapes on the sides (2 on each side) to make a better seal, but I've heard of people not doing that and never having issues. It's all personal preference: whether you can deal with the thought of a POSSIBLE leak or if you trust in your judgement and skill of cleaning up the area and torquing it down to the right spec.

If you meant the head gasket, generally people replace that since as Optimus mentioned: they're crush gaskets. They crush and flatten depending on the torque they've been squeezed between due to the bolt torque applied. Once they're crushed, they do not "bounce" back...so IF you were to re-use it, when you put it all back together, you'd have to make sure you torque everything down more so you can crush the gasket even more, producing a proper seal so no oil/coolant enters the piston chamber. It's peace of mind to simply replace it though. It takes a good amount of work to get that far into the engine.

 

guys... he said headers, the pipes your exhaust go through.

 

Good point Trippmann. I have been working on my cylinder head latley and must have had that on my mind when I read 'headers'.

I haven't changed the exhaust gaskets on mine when putting the headers back on. I just make sure they seat nicely on the old gaskets and torque them up to spec.

 

I would just change the exhaust gaskets... they aren't THAT expensive.

 

I've seen quite many of those rip when the header is removed. Sometimes it's partly burnt itself into the header or the head, and won't come off in one piece. If it looks legit, it can be reused, if it looks bad, replace. But as others stated, it's not that expensive so if you are going to go through the trouble to take it apart, why not replace it. Your post doesn't explain are you going to change it just because, or are you taking the headers off for a reason...