In the LB7 engine, the fuel lines entered the engine through the valve cover and actually sealed to the injector inside then engine. GM found through development of the initial engine that if fuel entered the engine, then a runaway condition could develop. So to prevent fuel from entering the engine should a leak occur, they sealed the bottom of the fitting with an oring, which is down inside the engine, you cant see it assembled. That would force any leaked fuel up wards and it had to go outside the engine, The nut that tightens the line down presses against the backside of the fitting applying pressure, so to get fuel past that, they cut grooves that run parallel with the injector to allwo fluid to go past that and outside the engine. Unfortunatly, it also allows all that crap back down in there which causes that pitting that we typically see.
Now, In the LLY system, the fuel lines connect outside the engine, thus eliminating a need to allow the fuel to exit that area. The line does not have those grooves in it and therefore, nothing can get down in there and sit.
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