I was thinking about picking some up and then I got to thinking. Will these really seal or is this a gimmic?. Anyone have any experience with these?

 

If you use the correct procedure, then those cheap cardboard gaskets will seal.

If you don't, then nothing will.

The procedure is: Carry a wrench for tightening your header bolts.

When you put your headers on, tighten up all your bolts to "nice & snug", but not "silly tight". You'll know by feel the difference.

Run the car for 5 minutes, then let it get dead cold. Retighten.
Run the car for 10 minutes, then let it get dead cold again. Retighten.

After that, every time you want to go somewhere in your car, check your header bolts and snug up the loose ones BEFORE going anywhere.

Do this until you fail to find loose bolts three times in a row. This will only take a few trips. Less than 5 before you stop finding loose bolts.

Once you are done with this, you are done. Period.

Check them every couple of months if it makes you feel better.

 

Putting copper next to aluminum isn't a good idea either. Look here.
http://www.engineersedge.com/galvanic_capatability.htm

 

I could not get them to seal with my headers, they leaked horribly.

I threw them out an went with the normal felpro set which sealed up fine.

 

I'd rather just use the regular felpro's