3406e keeps frying one cylinder

I realize they are custom, same principle as de accepting one. I'm pretty sure that number on piston packs is a 15.8 liter assembly. I could be wrong. Memory isn't as strong as it once was, and all my stuff is home I'm in Shreveport. Are you sure the machine shop is on the money here

 

Its definitely building a fire and getting hot if the rings are trashed. If it was a lube issue rings usually survive that

 

I am not the go to guy on these but that really sounds like an electric problem to me. It is possibly caused by over fueling and or out of time injection. Had a Detroit that ran funny, on every other cylinder, for several years, when started below about 40 degrees. It had multiple drivers and some said it knocks some times, never heard it and no codes. A driver brought it in one day and said it knocks very bad at times. When on start up turn it off and restart and it stops. When going down the road and it starts doing that let off the throttle, turn off the key for about 15 seconds and turn it back on, knocks gone. I have never heard a fuel knock like that in my life. If you were standing next to a front tire when it was started you would run for fear of your life. Turned it off and restarted, it run perfect. Bad ECM and sounds like you may have a different version of this.

 

Ok, here is what I think is going on. You have twin acert turbos on it right? With c-16 pistons and a marine cam if I read the post correctly. That much boost with alot of fuel is making the skirt swell up. Did you also use the c-16 crank? I willing to bet your air intake temp is getting up there. The piston skirts can take only so much heat. With the 5ek having the water jacket going into the center of block instead of the rear of block the water isn't pulling the heat away from 5 and 6 cylinders as well. You can do a few things. Connect s high pressure hose in one of the plugs at the right rear of block and to the rear cooler neck, that will help flow some coolant to 6 and 5 cylinders. Or install an Acert crank with low comp one pc steel pistons. Or programing or a larger cac to keep the air intake temp in check. Heat is the issue here.