Idle problem on C15 261 CU IN

[TCLARK]

I'm using AC plugs with an r in front of the number meaning they have built in resistance, that could be a problem.
I haven't yet hooked up a vac guage, my vacuum line is original steel and needs
to be tee'd.
The rpm flutters at idle at odd intervals about 2-5 seconds apart, I do have a new
plastic in line fuel filter, that is not plugged.

The carb is original to the 1959 261 engine,it has no gas leaks, but I didn't
check for warpage. I saw on you tube that warpage can be a problem.
Bob where did your carb come from?? What year an d model of vehicle,
I wouldn't mind finding one.
I will tackle this again tommorrow