Odd Exhaust Port Anomaly

[hocka09]

Hey Tuners,

This one has me stumped, folks. I’m currently pulling apart an engine I’m swapping from one car to another for a freshening up and I came across a single exhaust port that has nearly no carbon buildup, while the others have what I consider typical buildup. I went ahead and pulled the plug on that cylinder and it looks a little light but not glazed or anything indicating a lean condition. Unfortunately, the engine was already out of the car otherwise I would have compression tested it.

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A little history on the engine, it has a factory short block (~157,000 miles) and I pulled the head and had it completely rebuilt about 40,000 miles ago. I can’t say I noticed anything odd power/combustion-wise. Wideband O2 readings usually looked fine. Was basically running factory power on a 14b with ECUFlash tuning to get the fuel a little leaner (pig rich on stock cal).

My ideas are either reeeeeeally bad rings basically blowing by all combustion on that cylinder (no PCV oddities though) or clogged injector on that cylinder either completely shutting off fuel of causing a lean condition.

Any other ideas?

 

[motomattx]

Coolant in that cylinder.

 

[hocka09]

Coolant in that cylinder.

Ok, I was suspecting that but the gasket didn’t look like it failed. I suppose a new gasket, clean surfaces and ARPs will resolve that.

 

[ThunderChild]

I agree with @motomattx , that thing is way too clean and the car ran good for way to long for it to be a clogged injector. If the gasket showed no signs, then I'd start wondering about a crack somewhere, but if it was a factory hg, it's probably a small leak.

What's the intake port look like, just out of curiosity?

 

[1990TSIAWDTALON]

Steam cleaning from a coolant leak as stated. May have been small, but any water/coolant will clean the cylinder like that. What did that combustion chamber look like? Squeaky clean I would suspect.

 

[hocka09]

Here’s a photo of the intake port for that cylinder:

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Looks normal to me. In addition, here’s a photo of the cylinder head:

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There’s a bit of a sludgy carbon buildup. That cylinder had a decent amount of carbon buildup on the piston top as far as I remember, so that doesn’t really line up with the exhaust port. I think I will just chalk this one up to poor head gasket seal. I’ll also verify no cracks, good point there.

 

[1990TSIAWDTALON]

If water/coolant was in a cylinder, it would look a lot cleaner than the rest....usually......., so this is a strange situation.......
Anybody else have some advice to add to this???

 

[bastarddsm]

Is the head ported? Water leak in the port....

 

[Vegas Smith]

You have a self-cleaning head and you're complaining?

 

[hocka09]

You have a self-cleaning head and you're complaining?

Hahah I like the optimism!

Is the head ported? Water leak in the port....

The head is completely stock, no porting or anything. This encourage me to give it a good look over for cracks in that port though.

 

[pauleyman]

Crack in that port. Have the head checked