Trailerpro

Hope someone here can help me out. I built a 351w, and after finally getting everything put together, it ran great for the break-in. Sitting still, it runs and sounds great. Problem I'm having is when I'm driving it's backfiring out the carb, but only while accelerating. Timing is set right, all vacuum lines are new, new fuel tank, lines, filter, complete new motor, trans, carb, etc. I'm bangin' my head on the wall now trying to figure out why it won't do it while sitting still in my shop, but as soon as I get on the road, Pop.


Anyone have any ideas to help a youngster out?

Thanks!

John T.