C-15 6NZ fuel knock??

Well turns out the head is bad after all. The machine shop didn't check anything on the fuel side. The injector isn't getting a good seat and is getting combustion past the injector (makes since why it sounds like an exhaust leak). Cleaning and brushing out the bore and changing the injector cup and limp it along for a little while longer since work is busy and get a head on the way. Thanks for all the help!

 

My fuel pressure started to bounce with the knock because another injector o-ring blew from the combustion getting past the injector. If you pinpoint the noise with a stethoscope so you know what hole it's coming from then pull that injector you'll probably find a burnt or blown blue o-ring. Mine got bad enough that it left a carbon trail where it wasn't seating. But if its not obvious look down the hole with a scope (schucks has a good one for $120) and you'll see where it had been blowing past. You can also see it on the injector. Spray the bottom of injector off with brake cleaner and you'll see a discolored spot where it was blowing by