Black oily soot in intake system

[VegasZ31T]

Just removed the heads after experiencing a head gasket blowout with my 85 VG30ET.

There was black oily soot (equally on everything following) on the center of all the piston tops, in the intake runners of the heads, in the intake manifold, and in the lower portion of the plenum. The plenum intake was clean as was the upper part of the plenum, so it looks like it is caused by blow back.

I change the oil every 10 hours (autocrossing only - so maybe only 1 hour under load – the rest idling or at low revs), and have not had to top off the oil in between oil changes.

Engine rebuilt 49 hours ago.

Stock valves, Schneider 120# valve springs.

EGR is disconnected from the intake piping, and just vented to the air – a catch can.

Leak down test: 8% ON # 2 (exhaust valve), Less than 4% on the rest.

Nistune is installed: calls for 20 degrees advance on the distributor, and adjusting the spark advance via Nistune after that.

Russ’s adjustable cam gears: set at 5 degrees (maxed out) advance.

NISMO Euro cams; not much more overlap than stock.

Rocket 100 octane fuel.

14 lbs boost.

Any insights you can offer to identify and stop the oily soot deposits would be gratefully appreciated.

Edited September 7, 2012 by VegasZ31T

[Pharaohabq]

Black soot is usually from a rich running condition. Are you using a PCV valve? if you deleted, or if the filter in the valve was gone it could allow oil to circulate back into the intake making oily soot. If you are running FI, then a bad turbo seal could to it too. Since it's on all the cylinders I would expect it's either a leak in the intake, or more likely a rich running condition which is probably nothing to worry about if the engine sounds good and isn't smoking.

[VegasZ31T]

Thanks for the feed-back.

 

Apparently it is nothing to be concerned about as I also received a personal email on the same subject:

 

"From my industrial engine experience it is a light load, rich mixture, poor ring sealing engine not thoroughly broken in. I assume your valve cover breathers are going into catch cans. We see this all the time in generator engines run under light or no load most of their lives. This condition will start to appear in as little as 20 hours of use. Can you take the car out for a long, loaded run? If not it’s no big deal, the oily deposits really don’t affect performance mainly cosmetic. It's tuff to keep a street car/autox turbo car from doing this as so little of its life can be run at full load, full boost. On a generator engine we'll hook up an artificial load bank to it and run it under full load for 4 hours to burn all of that crap off but then 20 hours of operation later it starts appearing again. Try to limit the idle time as much as you can-which you are probably doing now anyway and run the piss out of it whenever you can!"

 

So I will go with that!