black in exhaust port

[dberman]

Last week I pulled the heat exchangers off a car I bought recently. The exhaust ports of one of the cylinders was coated with black while the other 5 where a light grey color. See pictures below. Before I purchased the car I had a leak down test perform and all cylinders were about the same. I also pulled the plugs and they all seem to be in good shape. Does this crud indicate a oil leak in the valve guides or too rich a mixture ( maybe a problem with that fuel injector)?

Thanks for the help.

Dave

[cdrik915]

It seems to be :

-1- valve seal : oil leak
- 2- lean adjustment : you need to be more rich on my opinion.

Just my 2 cents.

[500_19B]

Looks like two (relative) extremes to me. I think a little black is normal, but that first pic shows a lot of built-up carbon, likely from a leaky valve guide. All of my cylinders looked like that (some a little less, but all with signigicant carbon build up).

I am doing a top end on my motor, but actually I could have left it for a while yet as the valve guides were not that bad in reality (car was not smoking), but in my case the engine was out for other work anyway...

I'd be more concerned that you MAY be too lean on the other cylinders, which if left untended, can lead to significant damage, such as burnt valve. However, I would wait for opinions that are more expert than my own.

[Glenntpr]

Just today my mechanic called me after he pulled out the exhaust to replace the gaskets. Same thing with my 911 SC. One of the ports looks like yours and the others OK.

Fixing the exhaust leak was on my to do list... Here is my impression in my situation in which I am not particularly worried.

owned my 1983 911 SC for two years. the car did not run well at all with a bunch of vacum leaks.... That was taken care off by Matt de Maria...... Issue two..... CIS replacement...... Men I bought a take off from a good running SC and implanted the whole air box/CIS system. Matt changed a couple of fuel injectos along the way.... Now good compression, leak down, car idles great, runs 90% better.....

Currently the car is at the shop as i write tackling the exhaust leak (3 studs broke, ouch!).
NEXT: car is going back to Matt de Maria for reconnecting the o2 sensor and finalizing with the CIS adjustment...... My 2c on the port is that the fuel mix was not to par, bad injectors, etc.... runs good, idles great, good compression, etc.... not worried. If I have to rebuilt one day, a 3.2 transplant will go instead. i like my SC motor and will enjoy it (97,000)....

Please let me know what you find......

[KTL]

That one port is not really bad. Do a search on here and you'll find MUCH worse. When you find what appears to be a big black hunk of cotton in your exhaust port, that's cause for concern. Your port is somewhat typical.

Not saying it is no problem and you'll never have to worry about fixing it. Just saying that i've seen a lot of my friend's cars exhibit the same thing and they keep on truckin' with no ill effects. You'll just have to do what most everybody else does. That is, monitor oil consumption and noise level. When you start using a quart of oil every 500 miles of easy driving, you've got some engine work to do. When you adjust the valve clearances properly and you can't get them to not be clackety noisy, you've got some valve guide work ahead of you.

[E Sully]

It looks like oil, probably just a bit getting past the valve guide. The used 3.2 I bought was a lot worse. I ended up doing a complete top end job, but you seem to have time.