Full lock issues on 62 Impala

Hi Everyone,
I have fitted a new 500 steering box conversion that I purchased from CPP and I also bought a new centerlink, pitman arm, idlerarm and inner and outer tierod ends.
The problem I'm having is when the steering is on full left hand lock there is a loud bang and the idler arm flips around to the front and the wheels are pointing in different directions. Everything is brand new from CPP and looks right.

Any help would be great.

Thanks Bruce

The problem seems to be when the steering is on full lock and you keep pressure on the steering wheel the box will just keep going and twist the center link until the idler flips to face the front.

thanks for any help.
Bruce