Solving backfire problem on passenger side

[azjulian]

Easy way to check if you have an exhaust leak (be careful its hot!) is to take a rag bunch it up and block the exhaust outlet on the side of the car - you should feel pressure. If you have a leak you'll hear air exiting from that point. If you have a helper at hand that person can track down where the leak is coming from.

In the past when I've found a leak and its gasket related, I've taken every thing apart, sanded down the flanges and used sealant - if everything is flat you don't need the bolts very tight to maintain a leak free system.

[speed220mph]

HSSS427: I hate to butt in again, but my car is also an ERA with slip-fit primaries. These may fit loosely when cold, but swell when hot to seal the joint. One problem that is created when a header leaks is the header and head errode around the exhaust ports under the gasket, ensuring that a new gasket will leak. I had to mill the exhaust-header mounting face on both the head and headers to fix the leak. You already know how The backfire on my engine was fixed by pinning the cracks in the old tunnel-port heads.

[azjulian]

just to answer your previous question on re-jet of the demon...

if you have ported your heads and changed cam, then you will have increased the airflow into your engine - its entirely possible that the ratio fuel to air is still correct to the setup that you were given - you just need to make sure that you are not running too lean.