Urgent help needed

[Big dog]

Can anyone please give me advise , I am replacing my injectors on my 3ltr gen 2 surf , I have the first 3 done but the last one furthest away from front I just can't get it started on the thread, I am trying to start it by hand but no joy , as soon as I try the socket on it it just doesn't grip , if I have slightly de threaded it is there a way I can clean the groove , do I need to drill it to clean the groove , please help , many thanks

[bryanisaoldgit]

have you dropped sumiin the hole
or a washer off the injector