The timing is moving up and down which changes the idle RPM. It will idle at 900 and then to 1300. It isn't surging. It stays at 1300 for 20 seconds and then it'll go down. Surging to me is constantly going up and down without a pause in between. Also, as the engine accelerates it feels really sluggish. It just started doing this. The timing is 10 degrees when at 900 and 25 when the idle go's up. The teeth on the distributor look fine and no abnormal wear. Could the springs in the distributor lose tension after only a few hundred miles? It's as if the springs aren't even there and the weights are doing as they please. Also, it doesn't matter if the vacuum advance is hooked up or not as it still does this. The distributor is an hei and the carb is a holley 3310. Please help.

 

Replace all your vacuum lines...its like $8. Buy at least 5 feet each of part numbers "65114", "65111", and "65112"...if I remember right (vacuum lines).

 

have you even looked around for a vacuum leak yet?

 

The advance springs are too light for the weights and/or the weights are stickingor loose. The carb needs a different power valve. The light (Advance curve kit) springs are way to weak and result in a unstable idle and timing curve.

If you limit the amount of advance built into the distributor by limiting the mechanical advance travel you will be able to run more initial timing with the same total timing at high rpm. Then the right spring to allow maximum advance travel at 3000rpm will be much stiffer and much more stable. Low end off idle responce will be much better too.
Select a power valve that will stay closed at idle.
If you have 5.5" vacuum at idle, in gear then use a 4.5" power valve.
Here is a way to determine how much initial timing your motor needs.
remove the carb and flip it over. Look at the throttle blades. reset the throttle blades so that just a little of the transfer slot is showing. Ir should look like a square.
do this for both the primary and secondary barrels.
reinstall the carb and don't touch the idle speed screw.
Temperairily lock out the distributor advance curve so it will not advance with rpm. Start the car and give it about 20deg initial timing with a light. let the motor warm up fully and adjust the idle mixture screws for best idle quality an vacuum. now adjust the idle speed by advanceing or retarding the timing and note what the motor needs to idle in gear at say 750rpm. Say its 22 degrees. now you need to limit the distributor travel to allow 22 intial and 36total.
or 14degrees travel. then just select a spring with the tension that allows advance to max out at 3000 and remain stable at idle. ( usually a medium spring pair)
On a holley 3310 be sure to use a functional PCV system as it is part of the carb's idle circuit and design.