Goo under intake valve

RVG8tor · #1 12-18-2013, 10:20 PM

I was finishing up my annual and was changing the spark plug so I took the opportunity to use my dental cam to look in the cylinders again. I did this before but was concentrating on the exhaust valves.

Today I looked at the intake valves as well and I find this black goo on the underside of the valves. I am not having any engine issues but wondered if I should be concerned. All 4 intake valves have the same look. I did keep the engine on a stand while building and would roll it 90 degrees and leave it for a while and continue this unit the engine and done a complete roll. I don't know if this might be related. I know did get some oil into one intake tube, it was then that I realized I was leaving the roll at each 90 point too long. I have 161 hours on the plane and it has been flying for 1 year.

Here is a picture, the camera is a bit damage, that is what the black streaks are from.

Cheers

Thanks for any help.

RVG8tor · #2 12-20-2013, 09:46 AM

Interesting, a lot of views but no comments, this is not the usual response time frame of VAF.

Cheers

rocketbob · #3 12-20-2013, 09:55 AM

Normal, its due to oil burning on the valve face from valve overlap.

RVG8tor · #4 12-20-2013, 07:06 PM

Quote:

Originally Posted by rocketbob

Normal, its due to oil burning on the valve face from valve overlap.

It is funny what one does not know or think of. It is nice to have someone with experience fill in the blanks of my engine knowledge. Just in a new learning phase now that I am flying.

Cheers

rocketbob · #5 12-20-2013, 07:16 PM

It also comes from oil being drawn between the valve stem and guide.

SHIPCHIEF · #6 12-20-2013, 08:35 PM

Bear in mind that an engine is 'not new' from the first start to the last. It's all about the mid-life condition, and how gracefully it ages.
We now have dental cams and engine monitors to go along with compression checks and oil analysis. Seeing it first hand is kind of new for many of us. Thanks for sharing.
These are a great aid to find problems early. Then repairs can be made and the useful life of the engine extended.
So get used to 'used but good' parts and how they look while in service.
Some power is lost when the valves and ports get coated with sludge and carbon, so this would have a negative impact on a race engine, but it's typical of an engine in regular service.