I got my new engine set up last week, and started up for the first time (an awesome feeling) with the help of my neighbor (a professional drag race engine builder). He avoids a lot of problems by waiting to put gas through it until after he's hooked up a timing light and cranked it over enough to get close on the initial timing. That way you can avoid the backfires and make sure you've got a spark. We ran a LITTLE raw gas into the carb and it fired up immediately.
