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02-09-2016, 08:43 AM
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Join Date: Mar 2006
Location: SoCal
Posts: 626
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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....

__________________
JD
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RV-7 N314SY (KWHP)
IO-360-B1B
CANbus based trim/flaps and electrical
Last edited by jdeas : 02-10-2016 at 04:22 PM.
Reason: Wrong Pic
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02-09-2016, 09:14 AM
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Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,189
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EDIT: Did not notice the pix were of intake valves. Deleted comments...
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Ray
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)
Last edited by Raymo : 02-10-2016 at 08:36 AM.
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02-09-2016, 12:06 PM
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Join Date: Mar 2006
Location: SoCal
Posts: 626
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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.
__________________
JD
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RV-7 N314SY (KWHP)
IO-360-B1B
CANbus based trim/flaps and electrical
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02-09-2016, 12:11 PM
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Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,189
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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.
__________________
Ray
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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02-09-2016, 03:32 PM
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Join Date: Dec 2014
Location: hilltop lakes' Texas
Posts: 135
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Exhaust valve question
Are you talking exhaust valves and showing intake valves? Pardon if I'm wrong.
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02-09-2016, 05:22 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by 8 ball
Are you talking exhaust valves and showing intake valves? Pardon if I'm wrong.
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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.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
Last edited by BillL : 02-10-2016 at 07:50 AM.
Reason: fresh look, hardened diagnosis
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02-09-2016, 05:29 PM
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Join Date: Aug 2009
Location: Lexington, KY
Posts: 454
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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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Dorfie
RV10 Flying, N245JM
2020 dues paid with a smile
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02-09-2016, 06:12 PM
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Join Date: Aug 2006
Location: santa barbara, CA
Posts: 1,682
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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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02-09-2016, 10:28 PM
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Join Date: Oct 2005
Posts: 1,516
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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 
__________________
Ernst Freitag
RV-8 finished (sold)
RV-10 Flyer 600 plus hours
Running on E10 mogas
Don't believe everything you know.
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02-10-2016, 08:15 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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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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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 02-10-2016 at 08:19 AM.
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