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  #1  
Old 02-09-2016, 09:43 AM
jdeas's Avatar
jdeas jdeas is offline
 
Join Date: Mar 2006
Location: SoCal
Posts: 634
Default Exhaust Valve questions

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....
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Last edited by jdeas : 02-10-2016 at 05:22 PM. Reason: Wrong Pic
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  #2  
Old 02-09-2016, 10:14 AM
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Raymo Raymo is offline
 
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Default

EDIT: Did not notice the pix were of intake valves. Deleted comments...
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Last edited by Raymo : 02-10-2016 at 09:36 AM.
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  #3  
Old 02-09-2016, 01:06 PM
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jdeas jdeas is offline
 
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Default 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.
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  #4  
Old 02-09-2016, 01:11 PM
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Raymo Raymo is offline
 
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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.
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RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, Dual PMags, Vetterman Trombone Exh, SkyTech starter, BandC Alt (PP failed after 226 hrs)
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
All lines by TSFlightLines (aka Hoser)
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  #5  
Old 02-09-2016, 04:32 PM
8 ball 8 ball is offline
 
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Default Exhaust valve question

Are you talking exhaust valves and showing intake valves? Pardon if I'm wrong.
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  #6  
Old 02-09-2016, 06:22 PM
BillL BillL is offline
 
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Quote:
Originally Posted by 8 ball View Post
Are you talking exhaust valves and showing intake valves? Pardon if I'm wrong.
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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Last edited by BillL : 02-10-2016 at 08:50 AM. Reason: fresh look, hardened diagnosis
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  #7  
Old 02-09-2016, 06:29 PM
Dorfie Dorfie is offline
 
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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
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  #8  
Old 02-09-2016, 07:12 PM
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erich weaver erich weaver is offline
 
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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
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  #9  
Old 02-09-2016, 11:28 PM
N427EF N427EF is offline
 
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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
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  #10  
Old 02-10-2016, 09:15 AM
lr172 lr172 is offline
 
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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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Last edited by lr172 : 02-10-2016 at 09:19 AM.
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