Vintage Cars: engine surge at idle, 1966 chevy impala, chevy impala

Question
Don, I have a 1966 Chevy Impala with a 283 engine/Powerglide trans.  The engine was rebuild to stock.  I replaced the 2 barrel manifold with a 4 barrel Edelbrock and bolted on a 4 barrel Edelbrock carb # 1403.  It ran smooth last summer but since I started running it this summer it has developed a surging situation only at idle.  I noticed rust in the fuel filter so I purchased new tank, gas gauge, flushed out lines  gas filter and rebuilt the carb.  However I still have the surging problem at idle.  It runs smooth on the highway.  I check wires, ignition system, plugs and did a compression test.  Everything checks out.  Any other ideas?  Regards,  Jerry

Answer
If some of the passages in the carb are blocked it can do this.  When you rebuit the carb, were you careful to blow out all passages and maybe even use a thin wire to make sure they were clear.  Or have the carb boiled?

Check the float level closely and make sure the float isn't getting partially filled or that the needle valve seat isn't working loose.

Check out the advance weights in the distributor to make sure they are working right, and make sure the vacuume system is not getting a leak somewhere.

Hope this helps.

Don