Took the other three pistons out this morning. Rain stopped play before I could take the top off the FIP or take the turbo off completely. It's been lashing it down ever since.
Here are some piston pics from piston No2 onward. (piston No1 was posted above last week)
On this piston you can see a band of carbon build up down the side with nice straight edges
It looks like the carbon build up is allowing the piston skirt, between the rings, to brown/scorch.
Piston No3
There is carbon build up on 50% of this skirt (ie around this side)
This is the other side of piston No3
No carbon on this side and between the rings is less brown/scorched. Fairly normal I'd say.
Piston No4
Carbon distributed around the skirt on this one. You can see sections where the carbon has rubbed off or not built up. Thick carbon on the crown may have been protecting those strips?
Big end bearings don't look great for 30K miles (IIRC that's how many she's done since engine rebuild)
No1
No2
No3
No4
A bit of polishing on all of them and some radial scratches.
Don't know what's been in there to cause the scratches. First recon turbo was very iffy. When I sent it back and told them it was carped they claimed they could see tiny metallic pieces when the took it apart. Claimed it was off the engine boring. They might have been making that up to excuse the carped turbo! The block was washed after machining.
Oil pressure valve held no rogue bits. The spring is 48mm long, so it has lost 20mm since I put it in. Unlikely to be the cause of the high pressure I noticed.
So, where is the carbon coming from? Burning oil coming in through the inlet manifold from the turbo? Or, burning oil that's coming up past the piston rings? Burning oil coming down the valve guides. They are worn, but I was advised that this wasn't an issue so long as new seals were put on.