my passenger side header has a bent flange on it and makes the engine backfire. i guess this happens when air is mixed with heat and fuel supplied when the engine rpm is returning to idle(compression). Not only that but i can hear valve tick too, which wasn't there when there was no leak. So what would be the best way to repair this? i could probably try to flatten it and put a copper gasket on there instead of a standard one that tends to burn off.

my valves probably need relashing too hehe

 

I don't think that's the cause of the backfire. Relash your valves, and try to repair the flange, then go from there. Think you can just hammer it out?

 

I'd be willing to bet that your exhaust leak is also causing the "ticking", and it most certainly can cause backfires. However, if you just recently adjusted the lash, that could be the cause as well.

 

For your flange problem, I'd recommend using Percy's dead soft aluminum haeder gaskets. They're re-useable, and can seal fairly large irregularities. At the very least, you could use Mr. Gasket "Ultra-Seal" gaskets, and double them up. I wouldn't use the crap, white paper gaskets even on a perfectly straight header flange! I agree with jtrescot, the ticking could very well be the leaky flange instead of a valve.