Hi Terry,
Thanks for the info. I wish I knew what the cause of the deposits was. I thought it might be oil through the PCV line, but I put a catch can in the line and it didn’t catch anything. Plus, I don’t consume much oil at all. If a lot of oil was going into the intake, I’d have to top it up regularly, and I don’t. These flat 6’s are known to burn a bit of oil. I’m lucky to have one of the few that doesn’t burn much at all. Earlier versions of this motor had a reputation for fouling plugs if not kept above 4,000 revs. Maybe all my stop and go driving in traffic is to blame.
I thought about a piston soak. That would be difficult. First, because it’s a flat motor, the piston tops are vertical. If I put anything on them, it would just run down to the bottom of the cylinder. A certain amount would soak past the rings and into the oil. The solvent would go where I don’t want it to go, and it wouldn’t stay where I want it to stay. Also, a couple of the plugs on this engine are very inaccessible. I’m a DIY’er for most of this stuff, but I always pay a shop to replace these plugs, due to the PIA factor. The plugs are also way down below the valve cover, i.e. the plug boots are about 8 inches long, to get past the overhead cams. It would be almost impossible to get any solvent in the plug holes on the inaccessible plugs. Even the accessible plugs would be difficult.
I think I’ve ruled out any internal damage. I’ve put a couple hundred miles on the motor, and its running fine. There is no noticeable drop in mileage and power is fine. I think the bang was either inconsequential piston slap or a hydraulic lifter starved for oil. I think the bearings are OK. Perhaps they got some accelerated wear, but no damage. The engine idles perfectly smooth, with no bottom end noises or vibrations. The bottom end of these motors is pretty bullet proof. I believe the bottom end in my motor is the same as the bottom end in the 400+ HP turbo motors. People regularly bump those up to 450, even 500, with no changes to the bottom end. There is also a supercharger add-on for my normally aspirated motor that bumps HP to 350 or so with no changes to the bottom end.
If something happened to the valves, the motor wouldn’t run well at all.
I hope to do an oil analysis soon. I’ve been considering that for my own education anyways. Now I have even more of a reason to do it.
I have my FP on order and I’m just awaiting its arrival.
Thanks again,
Tom