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  #1  
Old 04-04-2021, 06:56 PM
dougknight dougknight is offline
 
Join Date: Jan 2006
Posts: 115
Default obnoxious exhaust valve

Over the last six years I have watched #3 cylinder digress from 78/80 to 67/80 on the leak down test of my 0-320-D1A. Approximate hours of this range is 500 hrs TT in 2015 to 800 hrs TT in 2021. I always listen very closely at oil fill spout, air breather intake and exhaust as each cylinder is under pressure. #3 has been obnoxiously loud out the exhaust for the last 300-400hrs.
I'm thinking the trend is obvious and it is time to attempt lapping the exhaust valve before it gets worse. Just wondering what the brain trust would do.

doug knight
RV-9a , 90625
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  #2  
Old 04-04-2021, 07:12 PM
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n82rb n82rb is offline
 
Join Date: Jan 2007
Location: fort myers fl
Posts: 1,015
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Quote:
Originally Posted by dougknight View Post
Over the last six years I have watched #3 cylinder digress from 78/80 to 67/80 on the leak down test of my 0-320-D1A. Approximate hours of this range is 500 hrs TT in 2015 to 800 hrs TT in 2021. I always listen very closely at oil fill spout, air breather intake and exhaust as each cylinder is under pressure. #3 has been obnoxiously loud out the exhaust for the last 300-400hrs.
I'm thinking the trend is obvious and it is time to attempt lapping the exhaust valve before it gets worse. Just wondering what the brain trust would do.

doug knight
RV-9a , 90625
first thing I would do is to bore scope it, see what the condition on the valve is. if it shows a hot spot or not. if the valve has a good heat pattern, then it might be worth lapping it, but if it shows a hot spot I would be leaning towards a cyl overhaul or a new cyl. same for showing signs of erosion on the edge.

bob burns
RV-4 N82RB
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  #3  
Old 04-04-2021, 07:29 PM
dougknight dougknight is offline
 
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Posts: 115
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thanks bob. shopping now for a borescope. any good leads?
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  #4  
Old 04-04-2021, 08:00 PM
moosepileit moosepileit is offline
 
Join Date: Dec 2010
Location: Louisville, KY
Posts: 698
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VA-400-WiFi Bundle: Vividia Ablescope VA-400 USB Rigid Articulating Borescope Plus VA-B2 WiFi AirBox for iOS Tablets iPhone and Android Phone and Tablet.

If you use an apple device, this bundled or similar adapter is needed, for Android or Windows laptop, not needed if On-the-Go (OTG) works on your Android.
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  #5  
Old 04-04-2021, 08:06 PM
dougknight dougknight is offline
 
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Posts: 115
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Quick search on Bore scope and Tim Holmes you sold me. Going with the Teslong #Nts500b over the vivida 400. $135.99
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  #6  
Old 04-04-2021, 08:16 PM
dougknight dougknight is offline
 
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Posts: 115
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any suggestions on best lapping compound?

ok, quick search and this seems pretty generic stuff. will go with loctite #1777012 280 grit 20 oz from amazon for $10.59 unless I hear of better

Last edited by dougknight : 04-04-2021 at 08:32 PM.
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  #7  
Old 04-05-2021, 06:33 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,876
Default Just an FYI

Quote:
Originally Posted by dougknight View Post
Quick search on Bore scope and Tim Holmes you sold me. Going with the Teslong #Nts500b over the vivida 400. $135.99
I recommended this to my 10-Friend and it has much better resolution, but he was not totally happy with the lack of ability to point it where he wanted to see. I have the teslong borescope for firearms and it has fantastic resolution compared to my VA- 400. I just wish it had the high resolution of the Teslong. Too bad they can't be combined, after all it's just a camera with a wire isn't it?

I still think for this job resolution would be a big advantage for seat inspection.

Be sure you really clean well to remove all traces of abrasive.
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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.
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  #8  
Old 04-05-2021, 08:52 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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I would not lap a valve until I knew why it was leaking. Several reasons for a leaking exh valve and not all can be resolved with simply lapping the interface.
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  #9  
Old 04-05-2021, 10:54 AM
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akarmy akarmy is offline
 
Join Date: Jan 2005
Location: Auburn, WA
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Quote:
Originally Posted by dougknight View Post
any suggestions on best lapping compound?

ok, quick search and this seems pretty generic stuff. will go with loctite #1777012 280 grit 20 oz from amazon for $10.59 unless I hear of better
I think you can use most anything. I used this pack that had 120 and 220 coarse and fine.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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RV-8 - Flying!
RV-9A - sold

Dec 2020 Paid
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  #10  
Old 04-05-2021, 11:09 AM
theduff theduff is online now
 
Join Date: Jan 2012
Location: Fallbrook Calif.
Posts: 329
Default Leaking Exhaust Valve in Cylinder #3

Cylinder #3 seems to be the hardest cylinder on exhaust valves and guides due to heat and restricted top end oil flow on that side of the engine. I would look carefully at the valve as it seats and see if you dont notice a slight sliding of the valve as it closes. This tells you the guide is worn excessively and likely your problem. Unfortunately the only way to remedy this is pull the cylinder for repair.
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