Geoffrey

I don't think it really matters if it is one or all six. The engine needs to be removed and disassembled anyway.

cobalt

Bad luck,

There is another turbo owner that had similar problems with a very low mileage car. Bad fuel caused it to run lean and he cracked 3 of 6 jugs. I had never seen a cylinder crack down the side like that and it appeared all the cracks were facing the top of the engine if that makes sense.

I know of 2 non turbo C4's that have had top end rebuilds lately. Both were in the $11k range. Yours might cost more due to the nature of what was done.

Good Luck

Indycam

If only one is damaged , would you pull apart all six ?
If five of six are just fine , would you just fix the one ?

Geoffrey

You need to inspect the engine and make a determination from there. Assuming the engine was fine in every other respect, you could replace one piston and cylinder IF you can find one of matching cylinder height and piston weight of the originals. Hopefully the head is Ok.

Indycam

I would start the inspection with a leak down .
Are you thinking it needs to be , all six , pulled apart ?

Geoffrey

He already said there is a problem with #4 which is where the noise is comming from. I'd start there and make decisions as I went along.

Indycam

If a leak down was done and 5 of 6 were ok , would you pull apart the 5 ?

Geoffrey

If one is bad you will at least pull apart 3 of the 6. Depending on what I found and who was paying I might or might not pull the other side apart.

Indycam

And then if you found bad leak downs on the left side and the right side , you would know that all 6 are gunna get pulled ?

Dave R.

By the way, how would old fuel cause a lean-running condition? By clogging or gumming up an injector?

Indycam

fuel that sits around changes , the light stuff goes away , the heavy stuff stays . Now the motor is just running on the heavy stuff . Do you see it or should I go on ?

wsybert

My understanding is that when the "light stuff" vaporizes, your are left with a lower octane, less stable fuel. Plus, it will start to turn to varnish and leave undesireable deposites in the fuel system.

stevepaa

I think if he only has one cracked/faulty cylinder/head, one still needs to disassemble all the heads. Who knows if he has any broken rings from this?
I think it might be penny wise and pound foolish to do a minimum rework in this case.

Indycam

"Who knows if he has any broken rings from this?"
A leak down test .

"I think it might be penny wise and pound foolish to do a minimum rework in this case."
Fixing what does not need fixing is very foolish .
If he has good leak down numbers , why fix ?
Only fix what needs fixing .

Dave R.

Indycam, I see how fuel can change over time and this could reduce octane, which could then result in detonation or pre-ignition. That's not the same as "running lean", where the fuel-air ratio is lower than desired.

Geoffrey specifically mentioned old fuel resulting in lean running as opposed to detonation, and I was curious about that.