Carboning? We don't need no stinking carbon !
I have no idea... Neither does the GM hitters here ...
(i.e. Both service managers, area Rep., and shop foreman with 15 yrs driveline experience... And that's just one dealership... LOL)
But, I will share my observances about the issue since I have had 3 5.3's and one 4.8 , and have tinkered with them a lot ...
Some of this is speculation but if you connect the dotted lines they make sense...
I have known for some time that the new vortecs burn oil... Some a qt every 3K and some a qt every 1K ... All the guys I have talked to that burn bad (not blue out the tailpipe/pcv valve fix guys) babied their trucks the first month... I have had 4 of these motors and have ran them hard on accel and decel the first 50 miles or so, (NEVER RED-LINED THOUGH) and not a drop until my avalanche (it burns 1 qt every 3500 or so, but I haven't tried the pcv valve fix yet) ... I learned that the first 20 minutes of run-time (after cam run in) on motorcycle motors that you have to load the rings fore and aft using the cross-hatched honing of the cylinders as an aid to good ring sealing... Rings and bores cannot be perfectly mated 100% and that roughness will "mate" the surfaces ... I have seen guys baby their bikes and they have filthy oil in no-time due to the blow-by ... Also, when the piston goes upward, it draws some crankcase gasses with it, and if the ring seal is not good, it will "draw" some of this into the combustion chamber... This theory along with the rumor that GM has poor bore concentricity and piston slap leads me to believe that if you have poor ring seal, that it's not just fuel you are burning in the cylinder...
So, in short, it may be that if you have a ring seal problem that has excess tolerances, a light and easy break-in that didn't seal the rings 100%, and have to get de-carboned every 20,000 miles, then you might be an oil burner at the same time... A parallel may be drawn... The hard part to nail down is the fact that people need the decarboning at various times... What IS a given is that there is noticeable "piston slap" when the de-carboning is done because it's part of the "cold spark knock" TSB ... Truck is knocking, technician performs TSB by decarboning top end, and knock goes away for another 20,000 or so (on most trucks...lol) ... What gives?
Is it a carboning issue? Or is it a reverse blow-by issue? ... I couldn't tell ya ... But it makes you think ... Remember the older 350's? like the LT1 vette and camaro? ... You never heard of these buring oil or carboning up did you? ... Heck no... I pulled down a LT1 with over 100K on it and the rings were mostly shiny and the piston skirts weren't scuffed hardly at all... They had hypereutectic pistons and short lands too... But never "carboning" bad enough to alter a/f ratios ...
I will say that I have never believed that the plug wires on the new engines could be improved upon... But I'll share a story...
My avalanche has had what has seemed to be a wrist pin clatter on one cylinder when I listened through the driver's wheelwell after it was hot ... It came in and out intermittently ... I started listening to other 5.3's at the service drive, on the street, and anywhere I could... The all did it to some degree... I replaced my wires with Taylors about 5,000 miles ago... When I pulled the plugs, the ground electrode was black with carbon, but the center and insulator was pretty clean... I just pulled my plugs after 3K and the whole insulator, ground electrode, and bottom 2 threads are clean... The whole plug is white except the bottom 2 threads... And guess what... No more knock in the well when hot ... Is this coincidence? ... Uhhh ... I'll say that the oem wires are at about 600-750 ohms/ft ... and the taylors are 50 ... With the performance increase I felt going to new wires and the lack of knock, I am willing to bet a soda that the new wires are providing a better burn in the cylinder than before... Now, take a cruddy oem wire that starts new with 700 ohms resistance and add 20,000 miles ... I think you get where I'm going...
I will say, that I have ran this passed the guys at the dealership and they have all installed new Taylors on their trucks... (almost all)... They all comment that the 5.3 has no more lag on bottom and the response is better... I'm waiting to see if they need decarboning in the future... I guess in my wholly nuts brain of mine, that the increased ignition intensity may help burn "whatever" is getting in there that can at times cause buildup...
I am no longer running berrymans every 3K in the gas, and my truck runs beautiful at idle ... I used to be able to see and feel the choppy idle after about 3K and no berrymans... I would run a can through and the truck was back to smooth idling and snappy performance... This is coming from a guy who can feel a gnat hit the windshield... LOL... Call me crazy, call me whatever... But you asked, and I gave my outlandish slant ...
11H