Sorry to resurrect a two month old thread... but the problem is still there. I put in a phenolic gasket / billet spacer from Don at 4 Seconds Flat yesterday (in case I was boiling the fuel), and it still seems to have this backfire problem that seems to be tied to heat (by the way, for those who don't have the 4 hole spacer on a dual plane... get one. The throttle response is great!).

To answer the above poster, I am running 3/8 aluminum tubing all the way from the tank in the stock location. eight inch section of 3/8 rubber fuel line to the fuel pump (Carter mechanical, 120 GPM @ 6 - 8 PSI), three inch section 3/8 rubber from fuel pump to Edelbrock billet fuel filter, short 3/8 rubber connector to 3/8 aluminum tubing running up to the carb in the stock location (behind the alternator, underneath distro and over intake manifold). It's not running near the headers at all, and is about a 1/2 inch away from the block at the closest (below the distro). Other than that, fuel line is away from the block.

Would a braided line cut down on the heat soak (if there is any)? Also, I have a new (stock) vapor separator. Should I throw this in, and set a return line to the tank? Would this help at all (no return line now).

This problem has had me scratching my head for a long time now. Any help would be appreciated.