Hesitation when accelerating 258

[Gungho]

I have a 1978 CJ5 with a AMC 258 i6 / 4.2l . I recently put mc2100 carb and hei distributor. When I first acclerate in first and second, there's hesitation (almost stall) and a mild backfire. If I put the clutch back in, it won't stall and idles fine. After driving for awhile, the problem goes away. Any ideas?

 

[Torxhead]

First things I would check would be correct ignition timing and carb accelerator pump operation.

 

[Lumpy Grits]

Most 2100 issues can be traced to vacuum leaks at the base. A spray bottle of very soapy water will show you this.
Put a vacuum gauge on and see what the reading is.
ALSO- BOTH, idle mix screws must be turned out the exact same amount. If they are not-It throws the 'balance' off within the carb.
Put a wrench to the manifold bolts to be sure they are 'TITE'.
LG