I just had my 350 chevy from my 1969 camoro rebuilt. The engine will not start. It will rotate and will backfire into the carb. I first thought it was 180 degrees out on timing. That was not the problem. I have gone everything I can think of. I have removed no. 1 spark plug and felt the air come out on the compression stroke, removed the valve cover to make sure both rocker arms were in the position that the valves would be closed at tdc on no. 1 cylinder, I made sure it is firing to the plug, I even removed my newer distributor( that had been working before the rebuild) and tried my old distributor. no change. Can anyone help me with this problem?