Whats the advantage of copper head gaskets over composite?

It's for my flatty with Offy heads.

 

Thinner,for increased compression.

 

Supposed to seal better for higher cylinder pressures... high compression... bolower... nitrous... etc

Really difficult to get them to seal correctly. If you're off a little... they will leak. But once they seal they are sealed.

I probably wouldn't do it to a flatty.

 

also,they are supposedly re-useable,if annealed.

 

Only if going for the max, too iffy for long term reliability.

Aluminum heads have poor transfer area anyway, the thin gasket just makes it worse.

And then you have 3 dissimilar metals.