Idle Screw Adjust Backfire

[huntb]

I am using the throttle response method to fine tune my idle screws and feel like it is set right but when I blip the throttle up to about 4k she backfires. The screws are adjusted to about 3 1/4 turns which might be a little rich but I couldn't get good results going below 3 turns (but the backfire was gone). Anyone know why it might be backfiring?

[BigD_83]

Have you:

a) replaced those shims that you inventoried, and
b) sourced a new idle mix screw to replace the one with the broken tip?

[tkent02]

Clairvoyance is good.

[huntb]

Have you:

a) replaced those shims that you inventoried, and
b) sourced a new idle mix screw to replace the one with the broken tip?

Shims are in and in spec and idle screws have been replaced and are functioning as designed. The hole in the carb throat where the broken tip was is a little beaten up but not too badly

[BigD_83]

OK...

now the question is. Is it a true backfire (through the carbs) or are you firing through the exhaust pipes (potentially along with a flame)?

[huntb]

Through the exhaust (it is a 4-1) but I wasn't seeing any flame