Exhaust leaks, Any tricks to getting the HEs to seat properly? Options

[KaptKaos]

I have had my heat exchangers off and on now about 4 times, trying to make sure that they are seated and tight. I have checked the copper gasket, put in new ones and still I get popping or back firing on decel.

Tonight I pulled the driver's side and flat filed the tops of the HEs to make sure I have a good surface. Nothing drastic, just trying to make it flat and smooth.

Is there any trick to getting everything buttoned up properly?

[Challe]

Take them out, heat them as sww914 says, let them cool slowly (don't put them into water as a friend to me did (IMG:style_emoticons/default/wink.gif) ) , then install them
Heat makes the copper soft, pressure makes it hard... same thing is possible to do with the copper sealing to the oil plug if you don't have a new sealing at oilchange


EDIT: Don't reuse the crush washer, allways use a new washer at oilchange, I mentioned the method for the crush washer only as a example and what you can do when you are in some situation when you don't have a new washer (and the old one is made of solid copper), here in sweden we had regulations for asbestos since late 70s but there is of course other fillings in the market, those will not change with heat at all.

Sorry, I should have written something like this: "this procedure does not apply to the crush gaskets that have asbestos or some other filling, just the solid copper ones"