Hey guys I just put some Heddman Hedders on my 1971 Roadrunner 340, I put them on correctly and there is still massive air leaks that make my car run really rough. It backfires when I'm in the low RPM's and I just can't open her up. What do you think the problem could be? Do I need to replace the gaskets with copper ones? Thanks for your help.

 

I run the copper,seems to help.All headers are a pain in the ***.

 

I used the ones that came with my Dynomax ceramic coated headers and haven't had a problem and I know they're not the copper gaskets.