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Exhaust Valve questions

jdeas

jdeas

Well Known Member
Did a leak down and scope last night and had some questions given the difference in the intake valves. Cyl 1 and 3 I expected however 2 appears to have abnormal lead buildup and 4 is really cleaner than expected.
1 80/74
2 80/65
3 80/75
4 80/77

#2 was 80/73 on the first attempt so I don't put much stock in these numbers but the pictures seem to support what I am seeing in 2 and 4.

LOP testing shows the system well balanced and all plugs looked good. looking for thoughts on why #4 is so clean and #2 has a buildup and low leak down numbers.


*Chrome cylinders....
ExhaustValves_zps1gnnbpkv.jpeg
 
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EDIT: Did not notice the pix were of intake valves. Deleted comments...
 
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CHT's

Yes I do but #2 is the hot one, not #4
In cruise:
1 340
2 346
3 332
4 336

EGT's can't be trusted for absolute values but testing for LOP shows a fairly good match across the board for mixture.
 
I was going to ask about EGT next and suggest that maybe #4 is running leaner than the others - which it could be doing on the ground, where lead fouling is sometimes more prominent.
 
Exhaust valve question

Are you talking exhaust valves and showing intake valves? Pardon if I'm wrong.
 
8 ball said:
Are you talking exhaust valves and showing intake valves? Pardon if I'm wrong.
Click to expand...

Second the question - that said, #2 looks like it has a hot edge- and does not look like it is on the seat.

Hot temps and leakage on #2 needs to be investigated further. You can remove the plug in the intake port and stick a small vinyl tube in there and in your ear to check for intake leakage during leak down test.

If it is a carburetor system, then the one with clean valve could be getting a very wet-rich mixture and eroding the deposits. Kind of a long shot though.:roll eyes:

Re-look this morning, burning/overheating intake valves - there is a serious problem. Remove the heads. Lash too tight, or bad seat geometry on rebuild, or factory, or too many hours.
 
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Also thought #'s 1, 3 and 4 are inlet valves. #2 appears exhaust with bad leakage on right edge (VERY hot) and responsible for high blow-by. Listening for hiss at exhaust during compression check should clinch diagnosis. Likely worn valve guide on #2.
Johan
 
Exhaust valves are smaller than inlet valves; looks like the pics are of inlet valves. I don't think there is any significant issue with the valves.
erich
 
Agree with Eric, those are all intake valves and as far as I can tell
there are no issues of concern.
What you are looking for is non concentric heat damaged discoloration.
A discoloration that starts on the edge of a valve rather than in the center.
That would be the case if valve/seat contact was lost for a number of reasons and a rapid deterioration of the valve edge would show itself through redish
and black heat rings extending from the area of no valve/seat contact.
Interpreting valve damage is more art than science and only a lot of experience will enable you to determine what exactly is going on in your cylinders.
Identifying the correct valve is just the first step ;)
 
It looks to me that some of deposit build up has been breaking free in the #2 Cylinder and you may have some of those deposits stuck on the seat. These usually clear themselves over time. Assuming you are hearing the hissing in the intake system during the #2 leak-down, I would test it again in a few hours and you may find it back with the others.

Larry
 
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Agreed

N427EF said:
Agree with Eric, those are all intake valves and as far as I can tell
there are no issues of concern.
What you are looking for is non concentric heat damaged discoloration.
Click to expand...

I agree there does not appear to be any hot spots. What I don't understand in the larger spread in the visuals (Cy 2 to Cy 4). Mix seem close at cruise and I replaced the spider last year in the hope of keeping a balanced mixture at taxi power settings.

Intake #2 does appear to show some buildup near the intake valve seat. I'll retest that cylinder in 10 hours to see if the low numbers just go away.
ExhaustValves_zpsimwatzk4.jpeg
 
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jdeas said:
I agree there does not appear to be any hot spots. What I don't understand in the larger spread in the visuals (Cy 2 to Cy 4). Mix seem close at cruise and I replaced the spider last year in the hope of keeping a balanced mixture at taxi power settings.

Intake #2 does appear to show some buildup near the intake valve seat. I'll retest that cylinder in 10 hours to see if the low numbers just go away.
Click to expand...

I bet that your idle and low rpm taxi the engine runs rough and stumbles from time to time. Especially when hot.

If these intake valves don't look like the edges are hot, can someone provide a picture where you think they are?
 
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I think what Bill is alluding to is what I’m seeing also, I don’t want to put words in Bill’s mouth but what I see is that there is heat destress on some of these valves and are definitely not what I see every year when I look at mine.

#2 is clearly running hotter between 1 and 4 o’clock position then the rest of the valve. From your low numbers on #2 and everything I have read about this, I would personally be seeing this as the beginning of the end for this valve.

#1 is clearly hotter between 5 and 9 o’clock then between 12 and 4 o’clock.

#3 looks hotter between 10 and 12 o’clock.

#4 is in general running the hottest but it’s also sealing the best and its heat pattern is even.

So I’m not sure what to say about #3 and #4 but #1 looks like a problem building and #2 has a problem.

This is only my opinion and in that case if this was my engine I would be sending these photos to my trusted engine Guy at Lycoming and see what he thought.
 
I don't see ANY sign of heat distress, nor would it be expected on an intake valve. There is uneven buildup of lead oxide (?) on some of these valves, but so what. This can also be seen on the INTAKE valve in one of the pictures in the 2nd of the two Mike Busch articles, although the article is focused on EXHAUST valves, and for good reason, as that is where the problems typically occur. There is no resemblance between the appearance of the heat distressed exhaust valves in the Busch articles and the pictures in this thread of the intake valves.

erich
 
erich weaver said:
I don't see ANY sign of heat distress, nor would it be expected on an intake valve. There is uneven buildup of lead oxide (?) on some of these valves, but so what. This can also be seen on the INTAKE valve in one of the pictures in the 2nd of the two Mike Busch articles, although the article is focused on EXHAUST valves, and for good reason, as that is where the problems typically occur. There is no resemblance between the appearance of the heat distressed exhaust valves in the Busch articles and the pictures in this thread of the intake valves.

erich
Click to expand...

You are correct, these are intake valves and for that reason you may also be correct that this is not a problem, I agree it?s the exhaust valves that suffer the most problems, however, maybe not a problem but to my eye #2 does resemble the pattern in the article.

It would be nice to have a better look at the exhaust valves for fun.
 
Russ, yes I was trying to get a little self education going.

With a larger picture the indicators can be pointed out.

Intake valves can and do burn, and will look just like these, so save these pictures and JD will keep us posted on the progression. I have very rarely seen an intake valve burn on a liquid cooled engine, but it is not unheard of in air cooled engines. Usually it is either a valve lash too small or very poor original seat geometry or a combination. Statistically, it is the exhaust that goes first, thus the popularity of articles.
 
reposted photos

I reposted the photos, my first post has the exhaust valves. The top post on page two is the intake valves. I think the intake is simply covered with lead deposits etc but the exhaust valves have a white and somewhat burnt even look all the way across.
My biggest concern was the big change in the intake valve deposits cylinder to cylinder
 
chipf said:
What model borescope are you using? Those pictures are very good quality.
Click to expand...

I can answer that, as it's my borescope...it's the Vividia VA-400 that was discussed here on the forums a short while ago. I'm very happy with it.
 
Color?

OK, read the PDF's but nothing seems to address the odd color of these valves. If it wasn't for the perfect color of the #4 intake, I would think this was a camera anomaly. It look like something is cooking off the valve face, not that the valve is overheating..

For clarity, here are the 4 exhaust valves again.

ExhaustValves_zps1gnnbpkv.jpeg
 
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jdeas said:
I agree there does not appear to be any hot spots. What I don't understand in the larger spread in the visuals (Cy 2 to Cy 4). Mix seem close at cruise and I replaced the spider last year in the hope of keeping a balanced mixture at taxi power settings.

Intake #2 does appear to show some buildup near the intake valve seat. I'll retest that cylinder in 10 hours to see if the low numbers just go away.
ExhaustValves_zpsimwatzk4.jpeg
Click to expand...

Looking at both sets of pictures, I see substantially more deposit build up in #2. This would indicate a cool cylinder and is consistent with the low compression. #2 intake is the only picture showing the seat interface and it doesn't look clean. I would do the leak down again and listen in the intake to confirm that is where the air is going. My guess is on a bad guide or bad geometry preventing the valve from sealing properly.

EDIT: I just looked more closely at the #2 intake seat in the exhaust picture set. It's tough to say for sure, but I believe you can see the build up on the intake seat that is preventing the valve from sealing properly.

Larry
 
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jdeas said:
OK, read the PDF's but nothing seems to address the odd color of these valves. If it wasn't for the perfect color of the #4 intake, I would think this was a camera anomaly. It look like something is cooking off the valve face, not that the valve is overheating..

For clarity, here are the 4 exhaust valves again.

ExhaustValves_zps1gnnbpkv.jpeg
Click to expand...

I don't think the deposits are "cooking" off. I believe they are breaking off. The deposits on #2 are at least twice as thick as the others. When they get thick, they can separate. The oblong areas near the intake valve with no deposits are where the air flows in and the wet fuel keeps that area clean with no deposits.

Larry
 
jdeas said:
I reposted the photos, my first post has the exhaust valves. The top post on page two is the intake valves. I think the intake is simply covered with lead deposits etc but the exhaust valves have a white and somewhat burnt even look all the way across.
My biggest concern was the big change in the intake valve deposits cylinder to cylinder
Click to expand...

Actually, the exhaust valves look fine. Pretty even deposits except for the parts that have chipped off.
 
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