320 e1 engine problem (I don’t know what I’m doing)

[Crusty320]

Before I get into the problem here’s some background info: 1965 Datsun 320, original e-1 engine and a new carb. The carb should be working fine but when choke is out and and I start to accelerate it will start to make a hiss-ing sound and the engine sounds like it’s not firing on all cylinders or not fully firing. but it works fine when the choke is near to fully in, this is so wierd I don’t what’s wrong.(I would attach a video but I don’t know how)

[datzenmike]

The choke forces an over rich condition and is used when the engine is cold. This assures that enough gas is evaporated in the cold conditions to allow the engine to run effectively.

 

If the engine runs best when warmed up with the choke on this would tell me that it is making up for what's lacking in the primary circuit. The primary side is over lean and the choke makes up for that lack. This can be from an obstruction in, or part obstruction of, the primary jet.        

[Stoffregen Motorsports]

Vacuum leak? Is the carb tight against the manifold? Loose nuts?