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  #1  
Old 08-20-2022, 08:31 PM
Mconner7 Mconner7 is offline
 
Join Date: Feb 2018
Location: Bradenton FL
Posts: 269
Default Valve guide reaming results

650 hours since new Millennium cylinders. #3 stuck and bent the pushrod and had witness marks on the piston (pulled and headed to the cylinder shop). 2 and 4 had to be driven into the cylinder with a drift to ream the guides.

Here is what I got out of the guides with a reamer.
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  #2  
Old 08-21-2022, 06:53 AM
RV6-KPTW RV6-KPTW is offline
 
Join Date: Oct 2014
Location: Sebastian Fl X26
Posts: 233
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170 hours on a IO390. Just reamed #2 exhaust valve guide after experiencing morning sickness. Looks like the same stuff found on reamer and cleaned off the valve stem.
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  #3  
Old 08-21-2022, 07:01 AM
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Jetmart Jetmart is offline
 
Join Date: Sep 2019
Location: Windsor, Ontario
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Quote:
Originally Posted by RV6-KPTW View Post
170 hours on a IO390. Just reamed #2 exhaust valve guide after experiencing morning sickness. Looks like the same stuff found on reamer and cleaned off the valve stem.
I have read in general the symptoms of morning sickness but specifically to your 390 experience what did you notice? How long did it last? Did you see anything with the EGT's? How did you determine it was #2?
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  #4  
Old 08-21-2022, 12:37 PM
Mconner7 Mconner7 is offline
 
Join Date: Feb 2018
Location: Bradenton FL
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Quote:
Originally Posted by RV6-KPTW View Post
170 hours on a IO390. Just reamed #2 exhaust valve guide after experiencing morning sickness. Looks like the same stuff found on reamer and cleaned off the valve stem.
I reamed all 6 and they all needed it. If one is sticking, the others will likely need reaming too.
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  #5  
Old 08-21-2022, 12:59 PM
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DanH DanH is offline
 
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Location: 08A
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Quote:
Originally Posted by Mconner7 View Post
650 hours since new Millennium cylinders.....I reamed all 6 and they all needed it.
IIRC, Superior (specifically Bill Ross) is teaching the cause of guide sticking is not leaning properly, i.e. not operating in cruise with a high enough exhaust gas temperature. Many pilots do in fact shy away from the peak EGT region.

In retrospect, would you agree with Superior's position?
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  #6  
Old 08-21-2022, 03:21 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by DanH View Post
IIRC, Superior (specifically Bill Ross) is teaching the cause of guide sticking is not leaning properly, i.e. not operating in cruise with a high enough exhaust gas temperature. Many pilots do in fact shy away from the peak EGT region.

In retrospect, would you agree with Superior's position?
Another poster here. I have a Lycoming YIO-360-M1B (non-Thunderbolt) in my RV-8. I've had a sticking (not stuck) exhaust valve in Cylinder #2 happen twice, the first at 447 Tach Hours and then again at 1020 Tach Hours.

I purchased the RV-8 with about 210 Tach Hours on it. Since I've owned it I've leaned aggressively on the ground, use the Target EGT method for leaning in the climb, and run about 100F ROP at 72% to 75% power, or 75F to 100F ROP at WOT and 2450 RPM at higher altitudes. I do run LOP sometimes, but not extensively. I normally don't run at peak EGT.

The first time the valve was sticking, we reamed all 4 exhaust valve guides, but only Cylinder #2 was crudded up, the other three were clean. The second time, we just reamed Cylinder #2.

My previous RV-8 had a Lycoming IO-360-A1A (PV) with 10:1 HC pistons (modified by LyCon). I ran it much richer in-flight (and never LOP) per LyCon's instructions, to make sure there was adequate detonation margins. In the 1900 hours I flew that airplane, the engine never had a sticky or stuck valve. I know the current owner and the engine now has about 2300 hours on it, with no difficulties.
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  #7  
Old 08-22-2022, 08:15 AM
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BillL BillL is offline
 
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Location: Central IL
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Default Hmm Why #2?

Quote:
Originally Posted by RV8JD View Post
<snip>
The first time the valve was sticking, we reamed all 4 exhaust valve guides, but only Cylinder #2 was crudded up, the other three were clean. The second time, we just reamed Cylinder #2.
<snip>.
Carl, just curious if your baffles have a provision for the lower fin cooling on head #2? Just wondering if that is a variable as well as A/F. My Lyc YIO 360M1B GAMI spread is really small so would not think that would trigger it.
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  #8  
Old 08-21-2022, 09:35 PM
Mconner7 Mconner7 is offline
 
Join Date: Feb 2018
Location: Bradenton FL
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Quote:
Originally Posted by DanH View Post
IIRC, Superior (specifically Bill Ross) is teaching the cause of guide sticking is not leaning properly, i.e. not operating in cruise with a high enough exhaust gas temperature. Many pilots do in fact shy away from the peak EGT region.

In retrospect, would you agree with Superior's position?
I am not sure what caused them to carbon up. I seldom run more than 60% power in cruise and always lean as much as I can but without being injected I am limited to around 25 LOP on one or two cylinders, the rest are at or near peak. Mike Bush thinks its lead byproducts.
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  #9  
Old 08-22-2022, 07:00 AM
RV6-KPTW RV6-KPTW is offline
 
Join Date: Oct 2014
Location: Sebastian Fl X26
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Jetmart: I started observing a little vibration on first startup lasting 30 to 60 seconds. It did not happen on all first starts. Engine ran fine once warm. Engine shaking was the initial alert and EGT indicated the issue cylinder.

Check this thread and specifically post 24 -
https://vansairforce.net/community/s...8&postcount=24
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  #10  
Old 08-22-2022, 08:16 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by DanH View Post
IIRC, Superior (specifically Bill Ross) is teaching the cause of guide sticking is not leaning properly, i.e. not operating in cruise with a high enough exhaust gas temperature. Many pilots do in fact shy away from the peak EGT region.

In retrospect, would you agree with Superior's position?
I don't

I have 850 hours on the IO-320 in my 6A. I lean religiously in climb (150 ROP) and cruise (~30-40* LOP) and occassionally even climb LOP. I have also flown about 20% of those hours in winter conditions where CHTS are in the very low 300's. I don' think I have ever cruised at peak EGT. According to this theory, I should be a worse case scenario.

Last summer I built a wobble test rig and checked all Exh guides. All were on the loose side of the range.

I remain convinced that the build up in the guides is coked oil from excessive heat and not lead from too little heat. Just looks at the pics in this post. The debris is jet black, just like Coke, and not grey like lead. Sure, chemical analysis will show some lead, but that is only because the oil was carrying lead particles in suspension before it converted to coke in the guides. Also, lead converts to a gas around 1000* and therefore any lead exposed to the guides above this temp are a non issue. The area of challenge, is idle, where exh temps are below this. We have seen this for decades. Dawdle around at rich idle too long and the plugs foul with lead. What's the answer, run the engine up for a minute an lean it to get EGTs up and it goes away. IMHO, lead is too soft to build up in the guides. It also is a natural lubricant and wont stick to anything, except at VERY thin layers. Look at the plugs. The lead forms little balls that fall right out. No reamer required.

More evidence - This did not happen to auto engines, even in the lead fuel days. Auto engines flow more oil to the rockers and that oil cools the valve stem. Lyc has anemic flow to the rockers due to a poor lifter design (no bypass channel to send oil up the pushrod, like every auto engine has) and therefore stems runs hotter. When / if the stems reach critical temperature, the oil cokes.

Larry
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Last edited by lr172 : 08-22-2022 at 08:38 AM.
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