468 big block, solid mechanical cam 264,265 @ .050 with 630, 630 at 108 degrees. My buddy says 26 at idle but he has a VERY radical cam and it's his race car. Other than that I'm lost. I've read on other posts to start at 15 advanced at idle with mechanical advance plugged. Is that the same as a big block, I'm not thinking so. Where should I start? The reason for this post is that my car just started to not idle, it idled down till it died and it loves to backfire out of the carb from a start, and I need to start somewhere to trouble shoot.