what is this good for? is it good? and down sides or ups i should know about? also to help cover my header.

 

It helps to keep your header from heating up your engine bay. Keeps your header a little cleaner I guess. If you don't wrap it right and tight it can look like crap. You can use stainless stell zip ties to hold it on better. Thats pretty much all I can think of at the moment.

 

i recommend not wrapping it. there is more of a chance of it getting to hot then cracking. it also voids the warrnety on the header if you wrap it. you will find this true if you read all the paperwork that came with it. it's in the fine print. it doesnt really do anything as far as keeping the engine bay cooler. it's a miniscule amount. also, while it does "keep your header cleaner", it allows water to get around trhe edges where it is wrapped and will rott out your header over a short period of time. 1-2 years. i have a header on my car, and it's not worth wrapping it when weighing the PROs and CONs.

 

pros:
-lower engine bay temps
-looks freaking awesome
-keeps moisture away from the header, so it won't rust (assuming you wrapped/sealed it correctly)

cons:
-more likely to overheat and crack the header (but I personally have never heard anyone have any problems with cracking their header.... I'd assume if you buy a quality header, you should be fine)
-voids header warranty
-can lead to horrible rust if wrapped incorrectly (okay, so not horrible... actually, I can't see it being much worse than the rust without wrap)

that's pretty much everything I can think of off the top of my head

and if anybody wants to argue about whether or not properly wrapped and sealed headers rust, I can always bring up a link to a thread from d-series.org of a guy taking his header wrap off... the part of the header that was wrapped was spotless and the part that was left bare was rusted.