Picture of my Burnt Valve

[precopster]

+1 on all the above plus an O2 sensor. If you research the O2 sensor manuafacturer's websites (Bosch, NTK and Denso) you'll see that 120,000 miles is about the limit of a 4 wire sensor. (less for a 3 wire)

After that they lose efficiency due to the rare metal coating wearing off so it will run rich with no doubt at all if it's the original sensor.

[rspi]

Well, here are a couple of pics from my head removal.

Bottom of Volvo S70 GLT head.

PICT7985-s.JPG (54.82 KiB) Viewed 2342 times

Head gasket from a Volvo S70 GLT, Leaking

PICT7991-S.JPG (66.92 KiB) Viewed 2342 times

It appears to me that the head gasket in this car was replaced prior to us getting it 3 years ago. I also remember changing the cams seals 18 months ago and the cam seals that were in there were after market seals. So, this is what the bottom of the head looks like after our 50,000 miles, mostly grocery store (Kroger) and Exxon fuel, 91+ octane (mostly 93), Castrol synthetic oil for the past 24 months, and it does get it's share of "blown out".

There is NO sludge in the motor, passenges look clean and there has never been any lifter ticking. The exhaust manifold bolts were loose on the side closest to #1. Also, the studs came out of the head (grrrr). Cams look good and I hope things go back together as well as it came apart. Man, those head bolts were tight.

[rspi]

Oh, my guess is that I had a leak near #3.

[byeboy]

Well, as bad as my carbon is, at least my head gasket was doing its job (under the most pressing of circumstances!)...

[V850B5254T]

To the best of my knowledge, the only chemical that can dissolve carbon is Carbon Disulfide, - a chemical that you don't want to get near any part of your car .

The trick with adding some kind of water, - some opts for water with CO2, is widely known, but it do not dissolve the carbon.
It is more like a shock treatment that will cool the hot carbon deposits swiftly and thus make it brake away from the engines internal surfaces. These broken away parts or particles have only one way to go and that is through the exhaust and then into the cat.

I would suggest that tests with water injection with the purpose to remove carbon deposits should only be performed with the the cat removed.

oakey

[erikv11]

Theoretical chemistry aside, carb cleaner works on piston heads if you stop it from evaporating. Three cheers for empiricism ...