Surging big block

[mikes67]

Hope somebody can help me with this problem. I have a 67 Chevelle with BB 396 bored 30 over with a 800 Holley and other things to make it run good. Here is my problem when I take in first then shift to second the car starts surging so bad I have shove the clutch this happened in third and fourth, when I gain some speed it will stop if I slow to 35 mph it surges a little.
When you read this I hope you understand, if not let me know and I will do my best to explain it better. This surging is a real pain in the butt.
Thanks
Mike