Carbon Buildup question

[korn]

I'm doing my first head job; here is a pick of the Pistons... Is the white residue from burning coolant or is that just excessive carbon?

[korn]

More

Closer look...

[dnguyen1963]

The residue looks like mineral deposit and that can come from water so my suspicion is coolant. Carbon build-up would look black.

[TobyB]

Except.... water tends to clean piston tops. Whenever I've torn down a
water leaker, it is always spanky clean in the offending bore(s)

That looks like oil consumption, with the white stuff being the burnt offerings on
the very top that are actually catching on fire. It's hard to tell (oil is 'greasier' than
fuel buildup) but it doesn't look like overrich fuel buildup.

What symptom lead you to pull off the head?

t

[nando]

yeah, coolant turns to steam which is really effective at cleaning the cylinders. When my head gasket went, #6 was sparkly clean and 1-5 were black.

[digger]

looks like ash deposits from fuel and oil, do you use any fuel or oil additives?

what did the head look like? and the back of the valves? probably the seals leak a little

[korn]

The head had a "superficial" crack in it that the prior owner JB welded... Startup was challenging, but it felt to me like ICV/ vacuum leak I could never track down. Also was close to due for a timing belt...

So; I figure why not? I'm having a cam reground, and a new head that has been prepped. And will replace all the lines that look suspect.

[Old525i]

A new Febi cam is about $125 from Amazon. Buy the Febi rockers as well (AutohausAZ).

[Northern]

looks like the pistons in my M20. Ran great before the timing belt grenaded at the top of first.

[digger]

A new Febi cam is about $125 from Amazon. Buy the Febi rockers as well (AutohausAZ).

quality is pretty crap ive heard.

[korn]

I have Febi rockers in there... Reground the I cam to 272. Here's how she looks after brake cleaner, brass dremel brush and some elbow grease...

[digger]

They don't need to be spotless a thin uniform layer of carbon works a bit like ceramic coating it's a great insulator.