ngk UR5 2771 wont thread into hole

[Yah's 87]

Imma trying to install these and I notice the shoulder is shorter and different. Has anyone had the same pleasure im having trying to install these?

 

[Royal-T-Ltd]

Nope those are all i have run for the past 10+ years and never had an issue.... which cylinder are you working on? and have you gotten any to thread in?

aaron

 

[Yah's 87]

i just rethreaded the old one back in for now, i tried 3 different plugs, and then just stuck the old one back in there, #1 cylinder, theres a small plate that is a guard by the manifold that might be the concern. I used two different deep well sockets, one a spark plug deep well and a regular deepwell.