Zero lash is when you have taken up the slack between the pushrod and the lifter. You can tell by tightening the rocker arm and twirling the pushrod. Look in the Knowledge Base. There are a few links there that will tell you how to do it.
If you don't know what zero lash is that is probably your problem. I bet you tightened the rockers arms too much and your valves are hanging open.
The carb is a big issue as well. Get an 1850 Holley 600cfm carb on Ebay. You can find one for around $30. Rebuild it and use it intsead of the carb you have. The one you have isn't worth the trouble. It is an emissions carb and it was made in the dark ages of automobiles, (the mid seventies to early 80's). Junk it. It will eliminate a lot of problems in the future as well.
Here is an example: