Damaged valve guides?

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cowman57
Posts: 17
Joined: Sun Sep 22, 2013 11:34 am

Damaged valve guides?

Post by cowman57 »

I've been having some intermittent rough running engine issues at first start up which always clears up after a few minutes. The last time it happened the engine was shut down after 30 seconds and a cold number 2 and 4 cylinders were observed be feeling of them by hand compared to the other four. I assume I'm having some sticky valves, and by running some MMO with the gas should clear this up (haven't done it yet). The other day a local AI told me that it's too late now and there's probably permanent damage to the valve guides. Can sticky valves damage the valve guides?
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ghostflyer
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Joined: Mon Apr 21, 2008 3:06 am

Re: Damaged valve guides?

Post by ghostflyer »

Well in my opinion !!!!! I wouldn’t waste my money on snake oil [MMO] . No engine ,fuel ,oil company recommends its use.
How ever I would be considering reaming the valve guides out . Not to remove metal but carbon build up.the cylinders are not removed I do the Indian rope trick for ease of valve removal. If you havent attempted it before ,I would get somebody who has done it to do it for you or assist you . The cylinders do not have to be removed to do this job. Personally I now prefer to do it this way , far cheaper,a lot less work and the cylinders are held securely in position. The method has been extensively written on the forum.
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N2625U
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Re: Damaged valve guides?

Post by N2625U »

Had it happen to me a couple of years ago when I flew to Kansas. Same cylinders as yours it seems that when you have a stuck exhaust valve on the O300 it will affect the cylinder next to it. No maintenance at the airport was able to contact an old A/P who had retired years ago. I had two stuck exhaust valves he did one with the rope trick and walked me through the other. I learned a hell of a lot during that hour keeping my mouth shut and listening. He told me the tools to get and I ordered them when I got home. He was very particular about which valve spring compressor and guide reamer to get. By far the best hundred bucks I've spent in aviation was that hour with him.
Keep your speed up, Blackhawk on final behind you.
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DaveF
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Re: Damaged valve guides?

Post by DaveF »

I'd say bent pushrods, rocker arm or support damage, or cam damage is more likely than guide damage.
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3958v
Posts: 543
Joined: Tue Apr 23, 2002 12:00 am

Re: Damaged valve guides?

Post by 3958v »

I had a valve stick open a few years ago on my way to Blakesburg. A mechanic had the proper size reamer which we used on the guide. That cylinder has been fine ever since. Bill K
Polished 48 170 Cat 22 JD 620 & Pug
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Bruce Fenstermacher
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Re: Damaged valve guides?

Post by Bruce Fenstermacher »

I doubt you have any damage what so ever. I wouldn't let that IA work on it either.

I've had several stuck valves in my C-145s, A-65 and C-85 including 2 stuck open, one on throttle reduction while in flight. On Wednesday I'm assisting a friend free and clean a stuck valve on his A-65, the second we will be doing on this engine in less than 4 months. He's stating to believe me when I told him we need to clean all his valves.

I've never removed a cylinder to clean any valves, this Wednesday will be about the 20th valve I've cleaned.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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Joe Moilanen
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Joined: Sun Dec 28, 2003 5:45 am

Re: Damaged valve guides?

Post by Joe Moilanen »

One thing about our engines that I feel is imperative now that 100LL is our only fuel (other than auto fuel) is Leaning at all times except at full power. 100LL has 4-6 times the lead that good ol' 80 used to have. Our engines can't handle the lead like higher compression ratio engines can. As soon as my engine starts up I lean it as much as possible, just enough fuel so that it will run on all cylinders. I lean at all altitudes (not aggressively or lean-of-peak or any of that nonsense that should be done only on injected engines, best-power or slightly leaner is fine) and don't go full rich until short final for landing. As soon as landing is affirmed, it is back to leaned just enough to run. I also let the engine run for several minutes at 1000 rpm leaned-out before shutdown to let the differential engine temps normalize. I just had my engine majored two years ago after putting 2550 hours on it, cylinders too. The rebuilder couldn't believe how many hours I had on it. Even the crank was within factory tolerances after 4300 hrs TT. Things I attribute my good luck to: No more than 25 hrs (even with an F&M filter kit) between oil changes, fly for at least one hour every two weeks, pre-heat if below 40 degrees F, Warm up engine @ 800 RPM or less for ten minutes upon start-up, and don't take-off until oil temp is at least 100 degrees F. Never had a stuck valve or issue in 40 years. We have GREAT engines but they misbehave without some TLC. Maybe I'm just lucky!

Joe
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MoonlightVFR
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Joined: Sun Jan 02, 2005 5:55 pm

Re: Damaged valve guides?

Post by MoonlightVFR »

Enjoyed these post. Wisdom expressed.

I am going take notes

3 x 5 index cards
gradyb, '54 B N2890C
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