What's caused this in exhaust port

[Sensibleboy]

All other exhaust ports are black but this has clean patches on it.
Plugs on all 4 cylinders all match and are clean. Car runs fine too.

Any idea why this port is like this?

[GreenV8S]

Clean sometimes means water. Is it positioned where it could get more than its fair share of crank case breather gases, or any other way for water to get in there? It might be as simple as the engine not sitting 100% level and water drawn in with the air tending to puddle into that runner.

[Sensibleboy]

The engine is on Jenvey ITBs. Crankcase ventilation is through to a catch tank.
It's been a few years since the engine was last inspected but the Omex 600 ECU was remapped recently. So it's not clear if the missing soot is due to the ECU calibration pre mapping or not.

[tapkaJohnD]

There is a 'shadow' of the valve stem/guide in both ports.
So either the cleansing effect comes from the bore - as said failed head gasket and water
or the soot comes from leaking oil from the valve lubrication via the guides.

[stevieturbo]

And what do the rest look like ?

[Sensibleboy]

All the other 3 ports are black and sooty with no clean areas.

Not sure if it would matter but the last time the car was started it was run for about a minute only and the engine has been out of the car for a couple of months over the winter for me to change the cambelt etc.

Edited by Sensibleboy on Sunday 27th February 13:45

[Sensibleboy]

Cylinder 1

[Sensibleboy]

Cylinder 2

[Sensibleboy]

Cylinder 3

[Sensibleboy]

Cylinder 4

[Jazzy Jag]

With the right tools you can change valve stem oil seals without removing the head.

I would go cheap early and try this.
Alternatively, if its running fine, leave well alone.

Let it develop as the guy who taught me as an apprentice, used to say.

[stevieturbo]

If it has not been using any water, runs fine etc etc...I wouldn't be worrying too much about it.

It might be one cylinder running richer/leaner than the rest or something, but without individual cylinder monitoring you'll never really know this.

[Boosted LS1]

If the soot feels wet then the seals ar well and truly fked. Just more fked then they appear. I had a rover like that albeit eons ago. That said, your valve stems aren't carrying lots of damp soot like mine were and still look nice and hot. Carry on and see what develops.

[Sensibleboy]

Thanks guys.

One problem is that this car does so few miles and pre mapping it wasnt running perfectly. It's much better now. It's impossible to tell if it's using coolant because the car comes apart fairly regularly.

I've no way of knowing if the clean port is from before or after mapping. I changed the spark plugs before mapping but they looked fine on removal.

When it was being mapped the guy said he did see a misfire occasionally but it had gone before he'd even managed to process it in his head.

So I'll take you advice and just drive it!