Anyone use these on a street engine? I am considering using them to reduce compression when I swap on a set of small CC chamber heads.

 

It's tough to get them to seal the water passages well on a street motor.Possibly with some Hylomar sealant.If you want thin, use a steel shim type gasket.These are embossed around the water passages and are also very thin when compressed.I'm using these on my big block.
If you are trying to decrease compression, I think the aftermarket composition gaskets will be thicker when compressed than the copper.
-Rich-

 

Which type of composition gaskets? The deal is that this is my 406 so I am going to have to drill steam holes, unless I can get a really good 400 sbc gasket.

I take it you have heard about the same sealing issues? I have heard that Hylomar is a pretty good sealant though.

 

on my drag engines i use silicon rtv a thin layer on both sides , works good for me

 

You can use steel shim gaskets and some copper spray gasket stuff. That's what I'm using on my 305.

 

This post has been drug back from the dead...

I decided to go with Fel Pro 1014 head gaskets...I heard of varying success with copper head gaskets...I didn't want to risk it...